Kubota Diesel Mini Airboat - Will it work? - What Prop?

A general, non-powerplant specific, discussion on airboat technology, ie., hulls, rigging, polymer, etc..
waikiki sneaky
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Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by waikiki sneaky »

Hello everyone!
I just bought a mini airboat (10.5ft x 6ft hull) with a 3 cyl Kubota diesel (D1105). I took it to through the truck scales on the way home. The boat weighs 780lbs as it sits in the pics (everything but a prop). The engine only makes 26hp @3k RPM's, however it does make 52 ft lbs of torque at 2200rpm. Also this D1105 engine is also sold with a optional turbo as well, the turbo version makes 33hp and about 65 ft lb of torque off 5-7 psi boost from the stock turbo setup). I found some tractor pull forums that say you can use an ebay turbo on the factory kubota manifold and push way more boost. I was thinking with delivery valves, injector work, and the turbo this engine should be putting out around 50hp and around 100ft/lbs of torque pretty easily. Guys on the tractor pull forums claim they crank them up to 75-100hp (but I didn't see anyone providing proof). So, could this work? I know it won't be the fastest boat around but could something like this run dry with one person? And does anyone have any suggestions what prop might work? I have a few ideas for reducing the weight a little too.
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Gary S
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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by Gary S »

At this point you have to try. But I would be surprised if it ran dry.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by bhrJR »

I have wanted to do that for a long time so I want to see how it works. Being such a low hp and heavy motor you will need a lighter hull to balance out. I had an 0-84 35hp direct drive on a very similar hull and it had trouble getting on plane in deep water even with a few different props. Chances are you will not get the prop right the first time being there's not much to compare to. I would try an ultra prop full length with 4 or 5 blades since you have the torque.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by kwanjangnihm »

waikiki sneaky welcome to SA!

All of us airboaters battle the same weight to horsepower ratio so we can run the green grass, beat the black mud monster or just cruising the waterways!

Here are a few examples of similar weight aircraft engines. Good luck with you build! :salute:

O-200 100hp 190lbs
D1105 26hp 242lbs
O-300 145hp 268lbs
He'll cut your throat, baby, stick you in the back, drive off in your Cadillac.
He's more trouble than you think, he'll kill your sugar, leave you in the drink.

waikiki sneaky
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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by waikiki sneaky »

bhrJR wrote:
Fri Sep 25, 2020 6:56 pm
I have wanted to do that for a long time so I want to see how it works. Being such a low hp and heavy motor you will need a lighter hull to balance out. I had an 0-84 35hp direct drive on a very similar hull and it had trouble getting on plane in deep water even with a few different props. Chances are you will not get the prop right the first time being there's not much to compare to. I would try an ultra prop full length with 4 or 5 blades since you have the torque.
The engine should be at 40-45hp with just the turbo and the injection pump adjustment turned up. Also remember the diesel has a lot more torque than the 084. I have sourced the parts for the turbo, should be able to do it for around $500 (sourcing some parts used). The turbo engine is only 8lbs heavier than the non-turbo, so I will be adding power without adding much weight.

Also I talked to Mike at arrow prop, he was very helpful. Going to get a smaller prop adapter made to take a rotax prop.

Ive been on the tractor pull forums and they rev these little kubota engines to 5k rpm and beyond, so a 1.5:1 reduction would prob make this setup much better, that way you could rev it up to 4500 to break free on dry (hopefully) and get going and then the boat wouldn't be so fast at idle either. But for now I am going to see how it works with the direct drive since its already set up like that.
kwanjangnihm wrote:
Fri Sep 25, 2020 8:00 pm
waikiki sneaky welcome to SA!

All of us airboaters battle the same weight to horsepower ratio so we can run the green grass, beat the black mud monster or just cruising the waterways!

Here are a few examples of similar weight aircraft engines. Good luck with you build! :salute:

O-200 100hp 190lbs
D1105 26hp 242lbs
O-300 145hp 268lbs
My backup plan is to sell the diesel and put a small aircraft engine on it. I just think it would be cool to make the diesel work. I know it won't be the fastest, but it would be a conversation piece and a fuel sipper. Also I would compare this more with the briggs and kohler minis which are around 125lbs + reduction drive. The 242lbs for my engine is with flywheel and flywheel housing, mine doesn't have the flywheel hosing so its prob more like 230lbs, which compared to the briggs or kohler its less than 100lbs differance. And it will have way more torque than the briggs and kohler engines, so I am optimistically hoping that it will be at least as good as a briggs or kohler mini.

Briggs 35hp & 52ft/lbs torque 125lbs+ weight of belt reduction
Kohler 40hp & 61.5ft/lb torque 132lbs + weight of belt reduction
D1105T 33hp & 65ft/lb torque 238lbs (stock D1105T *Turbo Model with 7psi boost)
D1105T (w/ mods) 45hp & 95ft/lb torque 238lbs (theoretically with turbo and injection pump turned up)

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by kwanjangnihm »

Chuck has a lot of mini info on this site (use search function) Sadly he has passed. :( chuckitt@earthlink.net

viewtopic.php?f=57&t=10884&p=675903&hilit=mini#p675903

He'll cut your throat, baby, stick you in the back, drive off in your Cadillac.
He's more trouble than you think, he'll kill your sugar, leave you in the drink.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by duckman5849 »

What's the back story of the boat? Was it ever up and running or a project someone gave up on ?
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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by Slidin Gator »

Sneaky,

Perhaps the following will help. This graph is useful for comparing options against a known. The actual thrust values will likely be lower than shown in an actual airboat, but it provides a point of comparison.

I have a 250 Hp, 14 foot boat that weighs around 1,650 lbs empty and at least 2,000 lbs minimum loaded with one person. The boat runs a 72" 2 blade prop and runs dry well. This chart gives 1,100 lbs of thrust, so call it .5 lbs of thrust per lb of boat, gear and rider to run well.

There is another rule of thumb around here that calls for 8 lbs of boat maximum per Hp to run well. This rule of thumb matches up with the 250 Hp and 2,000 lbs figures, but does not account for the non-linear thrust to power curve.

Image
waikiki sneaky wrote:
Wed Sep 23, 2020 6:07 pm
Hello everyone!
I just bought a mini airboat (10.5ft x 6ft hull) with a 3 cyl Kubota diesel (D1105). I took it to through the truck scales on the way home. The boat weighs 780lbs as it sits in the pics (everything but a prop). The engine only makes 26hp @3k RPM's, however it does make 52 ft lbs of torque at 2200rpm. Also this D1105 engine is also sold with a optional turbo as well, the turbo version makes 33hp and about 65 ft lb of torque off 5-7 psi boost from the stock turbo setup). I found some tractor pull forums that say you can use an ebay turbo on the factory kubota manifold and push way more boost. I was thinking with delivery valves, injector work, and the turbo this engine should be putting out around 50hp and around 100ft/lbs of torque pretty easily. Guys on the tractor pull forums claim they crank them up to 75-100hp (but I didn't see anyone providing proof). So, could this work? I know it won't be the fastest boat around but could something like this run dry with one person? And does anyone have any suggestions what prop might work? I have a few ideas for reducing the weight a little too.
At present, you have 780 lbs of boat and motor, add yourself, a cooler, tackle box and some other crap and I am sure the total exceeds 1,000 lbs. To push that rig dry you are looking for ~500 lbs of thrust or more on the graph. You have a 6 foot (72") wide hull, so a 66" prop probably works well. From the curve, you will find that you are looking for more than 75 Hp to make the boat run like you want. With a 66" prop you would be looking to make that power up to 3,500 RPM.

So, the answer is, you got to do everything, start removing everything that adds weight and nothing else, go on a diet yourself and start adding motor parts until she is blowing smoke and ready for the tractor pull.

It's do-able, just not easy, probably why the last guy sold er.
I still think I-10 is the Mason Dixon line.
2013 Mike Stossel Boats, 13' x 7' deck over, IO-540, 74" NGQ less winglets.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by NorthWestFloridaBoy »

I like this project and I hope it works out. I'd make a reduction drive for it and try a water walker Cypress prop. If you don't go reduction, get an alpha or razor x, about 66" or 64" if they go that short and spin it to 3500-3600. Your basically gonna have to do like waterthunder did on his DD LS boat, get a short prop and spin the shit out of it. Maybe you can find a 3 or 4 blade warp drive that short for cheap. It would be worth your time to search on here for waterthunder and his direct drive LS boat. It's apples and oranges, but the theory is the same for you. Keep it light light light. Or, sell the Kubota and get an 0200 0r something comparable. Anyways, good luck and keep us posted no matter what, this stuff needs to be documented.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by waikiki sneaky »

I ordered a tachometer and a complete turbo setup off a D1105T. I just need to figure out a prop to try. A 66in would fit with about 2.25in to spare on the sides of the cage and about 3in from the stringers. Is this too big cause my boat is only 60in wide at the bottom?

Measurements from my boat:
Bottom of boat 60in
At chines 65in
At top 74in
duckman5849 wrote:
Mon Sep 28, 2020 3:13 pm
What's the back story of the boat? Was it ever up and running or a project someone gave up on ?
It runs now, just no prop on it. The guy I bought it from said he put a prop off his 6 cyl aircraft engine on it, but it didn't push it well (as expected).
Slidin Gator wrote:
Mon Sep 28, 2020 7:01 pm
Sneaky,

Perhaps the following will help. This graph is useful for comparing options against a known. The actual thrust values will likely be lower than shown in an actual airboat, but it provides a point of comparison.

I have a 250 Hp, 14 foot boat that weighs around 1,650 lbs empty and at least 2,000 lbs minimum loaded with one person. The boat runs a 72" 2 blade prop and runs dry well. This chart gives 1,100 lbs of thrust, so call it .5 lbs of thrust per lb of boat, gear and rider to run well.

There is another rule of thumb around here that calls for 8 lbs of boat maximum per Hp to run well. This rule of thumb matches up with the 250 Hp and 2,000 lbs figures, but does not account for the non-linear thrust to power curve.

Image
waikiki sneaky wrote:
Wed Sep 23, 2020 6:07 pm
Hello everyone!
I just bought a mini airboat (10.5ft x 6ft hull) with a 3 cyl Kubota diesel (D1105). I took it to through the truck scales on the way home. The boat weighs 780lbs as it sits in the pics (everything but a prop). The engine only makes 26hp @3k RPM's, however it does make 52 ft lbs of torque at 2200rpm. Also this D1105 engine is also sold with a optional turbo as well, the turbo version makes 33hp and about 65 ft lb of torque off 5-7 psi boost from the stock turbo setup). I found some tractor pull forums that say you can use an ebay turbo on the factory kubota manifold and push way more boost. I was thinking with delivery valves, injector work, and the turbo this engine should be putting out around 50hp and around 100ft/lbs of torque pretty easily. Guys on the tractor pull forums claim they crank them up to 75-100hp (but I didn't see anyone providing proof). So, could this work? I know it won't be the fastest boat around but could something like this run dry with one person? And does anyone have any suggestions what prop might work? I have a few ideas for reducing the weight a little too.
At present, you have 780 lbs of boat and motor, add yourself, a cooler, tackle box and some other crap and I am sure the total exceeds 1,000 lbs. To push that rig dry you are looking for ~500 lbs of thrust or more on the graph. You have a 6 foot (72") wide hull, so a 66" prop probably works well. From the curve, you will find that you are looking for more than 75 Hp to make the boat run like you want. With a 66" prop you would be looking to make that power up to 3,500 RPM.

So, the answer is, you got to do everything, start removing everything that adds weight and nothing else, go on a diet yourself and start adding motor parts until she is blowing smoke and ready for the tractor pull.

It's do-able, just not easy, probably why the last guy sold er.
Thanks for the info! What prop can I spin to 3500rpm? Most I have read or called about are only rated for 3k rpm. Kubota makes another model of this engine that comes governed to 3600rpm, the rpm adds a few extra hp. But I have also read that spinning a prop over 3k doesn't really help push the boat.
NorthWestFloridaBoy wrote:
Thu Oct 01, 2020 1:04 am
I like this project and I hope it works out. I'd make a reduction drive for it and try a water walker Cypress prop. If you don't go reduction, get an alpha or razor x, about 66" or 64" if they go that short and spin it to 3500-3600. Your basically gonna have to do like waterthunder did on his DD LS boat, get a short prop and spin the shit out of it. Maybe you can find a 3 or 4 blade warp drive that short for cheap. It would be worth your time to search on here for waterthunder and his direct drive LS boat. It's apples and oranges, but the theory is the same for you. Keep it light light light. Or, sell the Kubota and get an 0200 0r something comparable. Anyways, good luck and keep us posted no matter what, this stuff needs to be documented.
What props can I spin this fast?

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by waikiki sneaky »

double post please delete

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by Slidin Gator »

Sneaky,

Ultimately, you are limited by the speed of sound in air. As the speed of the prop tip approaches the speed of sound the blade is liable to explode. Further, as you get above 80% or so the blade efficiency starts to drop. The "Or So" part is very dependent on the actual blade.

The speed of sound varies, but let's use 767 mph, 1,125 ft/s from Wikipedia. This is 810,000 in/min.

A 66" blade is running 3.14*66 = 207.24 in/rev. So at 3,000 RPM the blade tip is running 621,720 in/min and 725,340 in/min at 3,500 RPM. This is 77% and 89% of the speed of sound respectively.

A wider blade prop is going to be most efficient at lower speed. Narrow profile blades can maintain efficiency at a bit higher tip speed to use the higher Hp that a direct drive might make. The performance of the boat varies significantly between the two and is a future consideration. The first is to figure out what you can squeeze out of the Kubota.

When looking to soup up that diesel, you are definitely looking for maximum power between 3000 to 3500 RPM, but would prefer to make max power at 3,000 as long as it is close to what you can get at 3,500. Further, you do not want to trade off much 2000-3000 torque to push power to 3500. Definitely no need to go beyond that range unless you can make gobs more Hp at 4,000 rpm, in which case a gear drive is called for.

As for props, first sort out the power/torque curve hot rod options and then we can figure out the best prop. Follow NWFBoy's lead on some research:
NorthWestFloridaBoy wrote:
Thu Oct 01, 2020 1:04 am
I like this project and I hope it works out. I'd make a reduction drive for it and try a water walker Cypress prop. If you don't go reduction, get an alpha or razor x, about 66" or 64" if they go that short and spin it to 3500-3600. Your basically gonna have to do like waterthunder did on his DD LS boat, get a short prop and spin the shit out of it. Maybe you can find a 3 or 4 blade warp drive that short for cheap. It would be worth your time to search on here for waterthunder and his direct drive LS boat.
I still think I-10 is the Mason Dixon line.
2013 Mike Stossel Boats, 13' x 7' deck over, IO-540, 74" NGQ less winglets.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by NorthWestFloridaBoy »

You ask what prop can be spun that fast, slidin gator did the math there for you, it's going to come down to length, plus the manufacturer s design and the props construction. Most manufacturers are gonna tell you you can't spin their prop that fast, but there are some that can do it. If you decide to keep it DD, then Rpm and boost are going to be your only hope what so ever . Turbo it and get the most power you can at say 3600 or so then get you a prop that's 62-66 inches. I know the old school warp drive blades are tougher than a 2 dollar steak, and I'm sure that racers have spun them up that high. I mentioned the others because they are narrow like a warp but much more modern in design so they might be better for you. I can't remember off the top of my head which one it was, but Dave (WaterThunder) said in one of his posts In the DD LS boat thread I mentioned (I am 99% sure it was that thread) where he stated that the alpha or razor-x, one of the newer narrow ones that either sensenich or whir wind makes but he traditionally runs sensenich that's why I'm leaning towards the alpha, anyway he stated that one prop kept pushing up to 3600 RPM and the other one quit Increasing in thrust well before that. The warpdrive has been around forever and they are deemed "noisy' compared to the more modern offerings, for that reason, and the fact that the blades are solid carbon they can be easily trimmed to desired length. You could probably pick up a 3 or 4 blade 70-72 inch warp for cheap, then cut it down to fit your length constraints. Your working on a project that hasn't been explored much, so you're going to be the guinea pig in that regard. Keep it super light. Strip everything you don't need to safely operate the vessel and you might get it to plane out in deep water but I don't see it running dry. I hope you stick with it, don't get discouraged. And if it doesn't work out, sell the Kubota and I'll come down and take the hull off your hands... Lol. Just kidding, but seriously, I'll take the hull if you decide to scrap the project. I need one bad for my next build.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by kwanjangnihm »

NorthWestFloridaBoy I think this is the post you were referring to! :salute:
NorthWestFloridaBoy wrote:
Sat Oct 03, 2020 2:12 am
I can't remember off the top of my head which one it was, but Dave (WaterThunder) said in one of his posts In the DD LS boat thread I mentioned (I am 99% sure it was that thread) where he stated that the alpha or razor-x, one of the newer narrow ones that either sensenich or whir wind makes but he traditionally runs sensenich that's why I'm leaning towards the alpha, anyway he stated that one prop kept pushing up to 3600 RPM
Davie GSO480 wrote:
Tue Jun 25, 2019 5:25 pm
Hi all.....been a while sense ive been on this board.

I also had Dave build me a DD LS.
The motor is a LS3 block
EFI holley system
430 CI, Chevrolet cnc heads.

Dave (Waterthunder) has a thrust tester, it will measure thrust output.....it makes 1100 pounds + At 3600 with the Alpha 66
Most straight valve 0-540 make 940 =/-, angle valve 1000 +if its 10-to 1
I was at the last Thruman outting......Black full deck,,,,,,,,Midnight Rider..

The prop is a 3 blade Sensenich Alpha,,,,,,it makes thrust up to 3600......at 66 inches
Right now Im running it at 68 Inches and turning it 3200.
It will run with most 0-540 boats......
Ill post up a couple pictures and race videos...
He'll cut your throat, baby, stick you in the back, drive off in your Cadillac.
He's more trouble than you think, he'll kill your sugar, leave you in the drink.

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NorthWestFloridaBoy
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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by NorthWestFloridaBoy »

Close but no. That one says almost the same thing, but the one I'm referring to is a statement by WaterThunder and he says that the alpha was the only one that was still increasing in thrust at 3600 and the others quit increasing at like 3200 or something. He has an engine stand that is mounted on a shaft and anchored by some pillow block bearings and a load cell, it's a thrust measuring apparatus and he's able to test engine, prop, pitch combos and get accurate thrust data. Anyways that's not important, what's important is we've determined which prop it was that is effective to 3600 and it is the alpha. Wanted to make sure of that because my memory isn't as reliable as I'd like it to be. First thing if do if I was in your shoes is get a a turbo, mount it and do whatever tuning you need to do to the injectors or whatever and then try to figure out roughly how much power your making at 3600, then call sensenich and figure how many blades and what length alpha to get. Go back and talk to the tractor pullers that boost the crap out of those engines and see if they can help you determine how much power you'd make at "X" rpm with "Y" amount of boost etc. And find out how reliable they are at even higher rpms. If it can safely turn 4500 or so rpm then you might be better off doing a belt reduction with a moderate ratio, then you'd be able to swing even more prop then you could direct drive at 3600 RPM. A 1.5 ratio at 4500 RPM will give you 3000 RPM at the prop and approximately 1.5 times the torque (minus mechanical losses from reduction). I hope it works out, but you still might be better off selling the Kubota and getting a little aircraft engine, c90 or 0200 or something proven that will definitely push it. I like when thinking goes outside the status quo, and I like seeing people innovate and try new things, but there is one truth here, one fact that is going to rule everything: You can't change or cheat the physics involved. At this point if I was you I would sit down with a lot of paper and a calculator, get all the data you can about the engine, talk to as many people as you can that have hot-rodded those engines and find out if it's going to last under these new operating conditions it's gonna be under. Take all the numbers you can get including your Hull and rigging weight and really figure out how much your power to weight ratio is gonna be, because if you don't have enough power to the prop it ain't gonna matter how much you want it to happen or how long winded I get typing this stuff or anything. The physics involved will dictate if it'll work or not period. You need to find out how much power you can extract RELIABLY from the engine. Because if you can get enough power to make it work, but the engine won't last for more than 30 minutes making said power then I don't think it's worth pursuing. That's gonna be the key, finding out how much reliable power you can get from the engine and then all of your other calculations are going to be made off of that. So that's the first order of business in my mind, if it'll make 75hp but only last 1 hour before it self destructs versus if you can get say 55hp and it'll last and last at that output level then the choice is clear, you've got a 55hp powerplant and all other calculations and decisions need to be made according to that figure. Those numbers I just said are just examples but you get the point I hope. Anyways, good luck and stick with it, you've got a LOT of research left to do. Research is going to be really important here so that you avoid spending all your time, elbow grease and money on something that is physically impossible. Research research research. If you can't tell I'm a research fanatic and the more you do on this the better the end result will be.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by NorthWestFloridaBoy »

"The 3 blade Alpha is the only prop we tested that work in the higher rpm band, the Saber stopped converting about 3100,,,,,"


That's the quote that I was referring to. And I was incorrect about whome said it. It was a quote by Davie GSO480.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by waikiki sneaky »

NorthWestFloridaBoy wrote:
Sat Oct 03, 2020 12:08 pm
Close but no. That one says almost the same thing, but the one I'm referring to is a statement by WaterThunder and he says that the alpha was the only one that was still increasing in thrust at 3600 and the others quit increasing at like 3200 or something. He has an engine stand that is mounted on a shaft and anchored by some pillow block bearings and a load cell, it's a thrust measuring apparatus and he's able to test engine, prop, pitch combos and get accurate thrust data. Anyways that's not important, what's important is we've determined which prop it was that is effective to 3600 and it is the alpha. Wanted to make sure of that because my memory isn't as reliable as I'd like it to be. First thing if do if I was in your shoes is get a a turbo, mount it and do whatever tuning you need to do to the injectors or whatever and then try to figure out roughly how much power your making at 3600, then call sensenich and figure how many blades and what length alpha to get. Go back and talk to the tractor pullers that boost the crap out of those engines and see if they can help you determine how much power you'd make at "X" rpm with "Y" amount of boost etc. And find out how reliable they are at even higher rpms. If it can safely turn 4500 or so rpm then you might be better off doing a belt reduction with a moderate ratio, then you'd be able to swing even more prop then you could direct drive at 3600 RPM. A 1.5 ratio at 4500 RPM will give you 3000 RPM at the prop and approximately 1.5 times the torque (minus mechanical losses from reduction). I hope it works out, but you still might be better off selling the Kubota and getting a little aircraft engine, c90 or 0200 or something proven that will definitely push it. I like when thinking goes outside the status quo, and I like seeing people innovate and try new things, but there is one truth here, one fact that is going to rule everything: You can't change or cheat the physics involved. At this point if I was you I would sit down with a lot of paper and a calculator, get all the data you can about the engine, talk to as many people as you can that have hot-rodded those engines and find out if it's going to last under these new operating conditions it's gonna be under. Take all the numbers you can get including your Hull and rigging weight and really figure out how much your power to weight ratio is gonna be, because if you don't have enough power to the prop it ain't gonna matter how much you want it to happen or how long winded I get typing this stuff or anything. The physics involved will dictate if it'll work or not period. You need to find out how much power you can extract RELIABLY from the engine. Because if you can get enough power to make it work, but the engine won't last for more than 30 minutes making said power then I don't think it's worth pursuing. That's gonna be the key, finding out how much reliable power you can get from the engine and then all of your other calculations are going to be made off of that. So that's the first order of business in my mind, if it'll make 75hp but only last 1 hour before it self destructs versus if you can get say 55hp and it'll last and last at that output level then the choice is clear, you've got a 55hp powerplant and all other calculations and decisions need to be made according to that figure. Those numbers I just said are just examples but you get the point I hope. Anyways, good luck and stick with it, you've got a LOT of research left to do. Research is going to be really important here so that you avoid spending all your time, elbow grease and money on something that is physically impossible. Research research research. If you can't tell I'm a research fanatic and the more you do on this the better the end result will be.
NorthWestFloridaBoy wrote:
Sat Oct 03, 2020 12:23 pm
"The 3 blade Alpha is the only prop we tested that work in the higher rpm band, the Saber stopped converting about 3100,,,,,"


That's the quote that I was referring to. And I was incorrect about whome said it. It was a quote by Davie GSO480.
Thanks! I just looked the Sensenich Alpha 3 blade up, looks like it would be a very good candidate for this boat. I did notice the smallest it comes is 65in. I wonder if that is ok since my boat is kind of narrow. I have read that you don't want to go any longer prop than the boat is wide cause it can create a stability issue.

In regards to research, I think I have read just about everything on the web that relates to this engine and hopping it up. Theses engines come in the Kubota RTV 1100, so theres some info on those forums but most people with those side by sides don't need that much power. The tractor pull guys seem to have the best info on these engines. Below are some factory HP/Torque charts for the D1105, D1105T (turbo), and D1105 (NA high RPM).

Stock D1105 HP/Torque curve
Image

Stock D1105 Turbo HP/Torque Curve
Image

Stock D1105 NA 3600RPM HP/Torque Curve
d1105 3600.png
Comparing the high RPM D1105 to a regular D1105. You'll see 29.1hp for the high RPM (at 3600rpm) or 26hp for the regular D1105 (at 3000rpm). Doesn't seem like much but its about a 12% increase in HP

When comparing the Turbo to the non turbo model. The turbo model puts out 32.8hp while the non turbo regular rpm engine puts out 26hp. Both at 3k rpm.

I have the stock turbo setup of a D1105T coming in the mail now. I think with just the stock turbo (at about 10psi boost) and adjusting the injection pump (just the rack adjustment) it should be close to 40hp and maybe around 80ft/lbs of torque (@3k rpm).

If I remove the governor and let it rev to 3600 my hp should go up around 5hp. This is a estimation based upon the naturally aspirated 3000 and 3600 rpm comparison. On a turboed engine these gains may be a little higher? Also as the RPM's go higher the torque numbers are going lower. So would it be worth it to go up 600 rpm if it gained me 5hp but say cost me 10 ft/lbs of torque? This situation is different than a DD car motor that would likely be going up in hp and torque at those rpm's.

I can still remove the injection pump and have it tuned up and have the injectors opened up some too. Also I can put a stock turbo cam in my engine or get my cam reground (but that will also require my pistons to by fly cut. The guy I bought my turbo setup from runs 70psi boost (on a much bigger turbo) and 7000rpms on his pull tractor, but thats only for seconds at a time and he said it pulled the head off once and he's gone through some turbos. I would think this engine would hold up to 4500 rpm and a reduction drive as long as you didn't hold it at 4500rpm for long periods. But if you rev up to 4500 to break free on dry and then cruise at 2-3k, I think that would last a reasonable amount of time. These motors run at 2500rpm all day when they are in a tractor running a pto implement.

Im going to see what I can get the motor to do. Depending on how far I can take that motor, it might get to the point that Ive got the most I can out of the motor without going cra$y and it may be cheaper at that point to get a lighter hull. If that happens I'll prob put a small aircraft engine on this hull.

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NorthWestFloridaBoy
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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by NorthWestFloridaBoy »

Ok, I think your on the right track now. If it'll turn 4500 in then I'd go that route and a little belt drive refuction. Like you said, run it up high to break free or get on plane then back it down to 3000 or so is what I was thinking. I used to have a Kubota b2400 tractor and you had to run it at like 2800 Ron to get any power out of it and to get the PTO to 540 rpm to run the mower on back. I put about 3000 hours on it with nothing but oil and filter changes and 1 set of glow plugs. It still ran like new and I'm sure it's still going strong today. The more I look at your research I'm leaning towards saying I don't think it'll run dry. I believe you can get it to plane out in deep water if you keep it stripped of any thing non-essential. I hope I'm wrong, but like I said earlier, you can't change or cheat the physics involved. That 65" alpha is gonna the ticket though and your best bet to get it to do anything. Another thing to think about are the harmonics of the engine. I know on that tractor I had that at idle the engine shook crazy but once you got it up in the RPM range it was smooth.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by waikiki sneaky »

I got my stock kubota td025 turbo setup put on. I rebuilt the turbo before installing it. Just need a prop now! I found a 66in 3 blade IVO prop used, I can prob get it for $200-$300, but its like 3hrs away. The 66in prop would give me about 2.25in clearance from the cage on the sides (which are the tightest spots). This seems like it might be a decent prop for this boat. Any thoughts guys?

If anyone has any other props for sale that might work on this boat please let me know.

Weight Update
780lbs boat weight
-17.5lbs (stock exhaust manifold, muffler, airbox, engine pulling brackets, and dipstick)
+14lbs (adding the turbo setup, weight includes lines and hardware)

So it actually lost 3lbs so far, but I still have to add my air filter and tractor stack.
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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by barhopper »

I wouldn’t waste the money on a Ivo. That’s old technology. I had a stacked Ivo 15+ years ago. It worked ok but nothing great. Had to really spin it to get anything out of it.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by Slidin Gator »

barhopper wrote:
Thu Oct 15, 2020 7:07 pm
Had to really spin it to get anything out of it.
Barhopper,

That's kind of the plan here, find a prop that runs reasonably efficiently at high RPM.
barhopper wrote:
Thu Oct 15, 2020 7:07 pm
I wouldn’t waste the money on a Ivo. That’s old technology. I had a stacked Ivo 15+ years ago. It worked ok but nothing great.
Barhopper is correct the IVO may not be the best option, but the used IVO sounds like a cheap option to get the boat running and see if it preforms anywhere near your expectations. If she runs, but could use tweaking, then it's time to spend money on the right prop. At a minimum a cheap IVO gives you a test bed. If the boat is a total pig, a different prop would just be lipstick.
waikiki sneaky wrote:
Sat Oct 03, 2020 3:39 pm

Comparing the high RPM D1105 to a regular D1105. You'll see 29.1hp for the high RPM (at 3600rpm) or 26hp for the regular D1105 (at 3000rpm). Doesn't seem like much but its about a 12% increase in HP

When comparing the Turbo to the non turbo model. The turbo model puts out 32.8hp while the non turbo regular rpm engine puts out 26hp. Both at 3k rpm.

I have the stock turbo setup of a D1105T coming in the mail now. I think with just the stock turbo (at about 10psi boost) and adjusting the injection pump (just the rack adjustment) it should be close to 40hp and maybe around 80ft/lbs of torque (@3k rpm).

If I remove the governor and let it rev to 3600 my hp should go up around 5hp. This is a estimation based upon the naturally aspirated 3000 and 3600 rpm comparison. On a turboed engine these gains may be a little higher?
So you won't know which prop works the best, but that IVO is adjustable so you can try it across a range of RPM's.
waikiki sneaky wrote:
Sat Oct 03, 2020 3:39 pm
Also as the RPM's go higher the torque numbers are going lower. So would it be worth it to go up 600 rpm if it gained me 5hp but say cost me 10 ft/lbs of torque?
You are not loosing torque, where do you loose torque? Did the turbo kit fall off or something?

You still hit peak torque in the operating range, higher RPM results in more Hp. At lower pitch the prop/engine is going to respond quicker because the Torque vs. Thrust curve for the prop decreases with decreasing pitch. It's a tough concept to gather up in one sentence, but think of lower pitch being equivalent to changing your truck's rear gear from a 3.73 ratio (high prop pitch) to a 4.56 ratio (low prop pitch). You are going to wind it out higher, but it is going to jump out of the hole.
I still think I-10 is the Mason Dixon line.
2013 Mike Stossel Boats, 13' x 7' deck over, IO-540, 74" NGQ less winglets.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by waikiki sneaky »

double post please delete
Last edited by waikiki sneaky on Thu Oct 15, 2020 9:06 pm, edited 1 time in total.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by waikiki sneaky »

triple post sorry!
Last edited by waikiki sneaky on Thu Oct 15, 2020 9:07 pm, edited 1 time in total.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by waikiki sneaky »

waikiki sneaky wrote:
Thu Oct 15, 2020 8:39 pm
waikiki sneaky wrote:
Sat Oct 03, 2020 3:39 pm
Also as the RPM's go higher the torque numbers are going lower. So would it be worth it to go up 600 rpm if it gained me 5hp but say cost me 10 ft/lbs of torque?
You are not loosing torque, where do you loose torque? Did the turbo kit fall off or something?

You still hit peak torque in the operating range, higher RPM results in more Hp. At lower pitch the prop/engine is going to respond quicker because the Torque vs. Thrust curve for the prop decreases with decreasing pitch. It's a tough concept to gather up in one sentence, but think of lower pitch being equivalent to changing your truck's rear gear from a 3.73 ratio (high prop pitch) to a 4.56 ratio (low prop pitch). You are going to wind it out higher, but it is going to jump out of the hole.
If you look at a dyno sheet you will see torque numbers will go down after a certain point and hp is going up till they eventually cross at 5252 rpms. On a small block v8 the torque numbers should still be increasing between 3000rpm and 3600rpm. However if you look at the hp/torque charts I posted for my 3 cyl kubota you will see torque peaks out around 2200rpm, and then starts declining. So I was saying I don't know if the effects of spinning at 3600rpm vs 3000rpm will be as great as when turning a small block at the extra 600 rpm.

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Re: Kubota Diesel Mini Airboat - Will it work? - What Prop?

Post by Slidin Gator »

Maximum Hp is roughly related to maximum thrust. If you will double check Your Kubota turbo curve (forget about V whatevers) you will see that Hp is close to peaking at 3,600 RPM. It does not continue to climb, it will be on the way down before it crosses torque at 5252. If you could build that Kubota to make power to 4,500 or more, then it's gear box time as discussed above. But we are talking direct drive here.

The torque curve defines how the engine/prop system responds, how quickly you build thrust when you mash the gas.

You are low on Hp and need to focus on that first, if we were talking 70 vs. 80 Hp it might be time to focus on area under the torque curve. Regardless, the only way to know is to try and see what sticks.

How much is this prop?
I still think I-10 is the Mason Dixon line.
2013 Mike Stossel Boats, 13' x 7' deck over, IO-540, 74" NGQ less winglets.

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