ECOTEC 2.0 LTG SWAP

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OneBFC
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Re: ECOTEC 2.0 LTG SWAP

Post by OneBFC »

Striker543 wrote:
Wed Dec 25, 2019 10:24 am
If you do research I think you will find you mount the engine as low as possible for maximum thrust. Having the tip of the prop below the transom does not lose any measurable thrust and having the engine lower gives it a much better push point.

This is totally true. High push point is something to avoid. It's never beneficial. It's the one area in airboat design that you aren't giving something up in exchange for something positive.

Set the engine height so the tips of the prop are 3 inches or so above the stringers in the hull.
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Re: ECOTEC 2.0 LTG SWAP

Post by FISHSTICKER »

I don’t disagree at all with what you are saying about best practice but i would think you would loose a lot of thrust. I always assumed the low side deck overs were probably an effort to get rid of the negative effects of having the prop in the boat.

Thanks for the input.

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Deano
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Re: ECOTEC 2.0 LTG SWAP

Post by Deano »

FISHSTICKER wrote:. . . i would think you would loose a lot of thrust
While it may look that way at a glance, the fact is that the air moves down the blade toward the hub before it proceeds aft to generate the thrust you are looking to generate. Even a lowly Direct Drive that can only turn a 72" prop does not loose a measurable amount of thrust by dropping the blade tips a beer can below the top of the transom. :idea:

To re-state the same premise in other words, an 80" diameter prop doesn't generate an 80" diameter thrust column.
As a percentage of total, there is little to no thrust produced at the blade tips.
Consequently, there is little to no measurable loss in thrust by dipping the blades below the transom.
Interestingly enough, this percentage of loss also gets smaller as the prop diameter and blade count get larger. :wink:
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Slidin Gator
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Re: ECOTEC 2.0 LTG SWAP

Post by Slidin Gator »

X3 on the advise given, your prop is an air compressor, drawing low velocity and low pressure air in from all around and compressing it to a higher pressure, high velocity stream near the hub. If you think about it, the area on the inlet side has to be larger than the exit area, otherwise there would be no thrust.

The Deck over gets some advantage from improved flow on prop inlet, but primarily makes the boat harder (not impossible) to sink and keeps the boat from filling with crap.

My 72” prop sits 5” below the transom lip. An item Darren at Sensenich pointed out to me, closer to the runners can lead to higher tip wear from grass and bailing water.
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: ECOTEC 2.0 LTG SWAP

Post by FISHSTICKER »

That makes sense. To test you guys I went cranked the airboat :D . Certainly much less thrust in the last 1/4 of blade length. So with a 76" wide blade maximus prop how much would you put below the transom? A 10 oz pony or a 16 oz tall boy? I'll call Andrew and talk to him to get his input. Thanks for the detailed explanations guys.

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hogdoggin
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Re: ECOTEC 2.0 LTG SWAP

Post by hogdoggin »

I'm with everyone else lower push point the better! You will lose very little if any thrust with the blade down in the hull. The higher the engine the worse it will roll over on the nose. You'll notice it way more on a shorter boat. I'd set the prop 10 inches off the bottom of the hull.

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kwanjangnihm
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Re: ECOTEC 2.0 LTG SWAP

Post by kwanjangnihm »

I had grabbed a bunch of input a while back on the same subject.

Transom Data (each line break is a different user input)

Mine I believe mine is 9 inches in the boat. I'm running an R series.

a lower push point will gain you more than any so called loss of thrust.... and by the way thrust is a byproduct of what the prop really does, and that is screw through the air... it’s the same as an out board motor prop in the water .... All you young guys that have never ran a wood prop, here’s how they used to gage a prop. a 72 -32 wood prop in theory would move 32 inches forward every time it made 1 revolution, the best thing you can do to help your airboat is to have un obstructive air feeding your prop no matter what kind it is.... plus the lower the center of push of your boat the less down force you put on the nose, I have my 70 in prop 10 inches below my transom

I've built and ran a lot of different airboats from ride to race boats, I can say that my best handling and performance boats all had between 10 to 12 inches inside the transom, handling and lower point of thrust far out ways any down side my boat right now has a 81 inch Sensenich 12 inches inside and it works.

Have mine 11 inches in , 82" R . The tips draw air in and middle of prop is where thrust generates. That’s the purpose of the winglets to cup air and force it toward middle and not escape off end.

11'' deep on a 16x8 marsh master. Works great. JMHO....

you should not have any noticeable loss in thrust, with only 7" below the transom. I have a boat with almost 12" below!!! And no considerable loss of thrust there. ( I have been told ) The boat has a 84" 3 blade R and is 20' + HEAVY, but will run dry loaded with 7 passengers!

i run mine about 9'' in the boat and 4'' from the stringers i didn’t lose any thing that matters and i dont need a pump the prop bails it just fine 82'' super wide..

The lower the better!!! Don’t worry about the prop being down below transom. The end of all props flatten out under RPM and give no push at all. Push comes from the hub out where all the pitch is. I will say again, simple test. Take a empty soda/beer can and put it on a flat surface. Take a finger and place it one inch from top and push it across table. Now do the same thing with your finger one inch from the bottom. Make cents? Anywhere below center is good, anywhere above center not so good when metal work is being built the most important performance thing is the height and location of the stand. If you can just slide a pencil between the end of prop and stringer, nail it. On a deck over between the prop and deck. Just one old man’s big "O". Former member "NARA",, rider, builder, tear um up, fixer since 1968. J Renney (ps all engine stands should be built with an up and down adjustable nose mount)

The number one reason to run your prop down in your hull is to lower your CG. In a car motor this makes a huge difference it’s not as critical on an aircraft because they run such a small prop. If you have an 80 inch prop 2 inches of your deck on a 15 sided hull the center of your prop is 57 inches off your bottom. This causes torque roll and plowing also the higher the motor sits the more it pushes down on the nose. If you run an 80 prop 2 inches off the bottom the props center will only be 42 inches from the bottom. That 15 inches makes a huge difference in how the boat performs. Most aircrafts run a 68 to 72 inch prop so it’s nowhere near as critical but it still helps. There is a direct correlation between downward force on the bow and engine height. Also when the motor is higher the boat will torque roll more. Due to higher horsepower levels car motor gearbox boats are the most sensitive to engine height. Two or three inches will make a very noticeable difference. With the carbon fiber props on a ride boat I keep the tip’s 1½ inch off the bottom on race stuff I try for 3/8 of an inch. Of course the lighter and smaller a boat is the more noticeable these changes are. So if you’re running a 16ft tour boat this height will not matter as much as a 13ft ride boat. The higher the motor the harder it is to keep them from riding on the nose and the more the boat will torque roll. Sometimes losing a 100lbs of thrust will drastically improve how a boat rides! You will not feel this so much on boats over 2,300lbs or over 16ft long but you build a light medium size airboat and those 6 inches of height will COMPLETELY change how loose and how well the boat rides!
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Re: ECOTEC 2.0 LTG SWAP

Post by FISHSTICKER »

So I can run my prop as deep as 14" down in the boat. Would any of you consider actually doing that? I see in the post above someone was running 12" in the boat. Since thrust center line being close to the bottom of the boat is important should I run a shorter 4 blade?

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Re: ECOTEC 2.0 LTG SWAP

Post by Striker543 »

My vote is to run as long of a prop as you can. If your boat has plenty of spare power you may find a shorter 4 blade feels more fun to drive, but my starting point would be the longest prop I could swing, then I’d experiment as time and money allowed

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Deano
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Re: ECOTEC 2.0 LTG SWAP

Post by Deano »

FISHSTICKER wrote:So I can run my prop as deep as 14" down in the boat. Would any of you consider actually doing that?
I see in the post above someone was running 12" in the boat
IMO, in your specific case the answer would be a definitive NO, I wouldn't do that.
As is true in many different cases, more of a good thing doesn't always remain a good thing if it becomes excessive.
It is worth pointing out, in that particular instance, the test subject was an 84" four blade prop, not a 76" three blade.

It's important to remember that:
Deano wrote: . . . this percentage of loss also gets smaller as the prop diameter and blade count get larger.
Realize that what is allowable or works well on a 20' boat w/an 84" four blade prop, will not necessarily be desirable on a 12' boat w/ a 76" three blade. Although the variables do remain the same, they are quite simply 2 completely different orders of magnitude.
FISHSTICKER wrote:Since thrust center line being close to the bottom of the boat is important should I run a shorter 4 blade?
Again, it is my opinion that I would not expect that would be the preferable option; although I don't exactly know the parameters under which you are operating (more on that toward the end). This question bears on different variables than do the previously mentioned ones.

Fundamentally, diameter trumps pitch where generating thrust is concerned. Consequently, it's the first variable that should be considered.
In our case . . . the boat and (then subsequently,) the cage width define this constraint for us. (Whoever doubts this premise need only spend some time trying to find a large helicopter running less than an 86" diameter prop. :roll: )

Where blade count is concerned, adding another blade will introduce two potentially negative aspects: First, there will be more ongoing parasitic drag due to increased total blade area which creates more 'overhead' before the desired increase in thrust can be realized or seen. Secondarily, it will increase the 'total mass' of the propeller which will primarily effect the 'snap' due to the additional loading put on the engine when it is attempting to quickly accelerate.

If any given blade count (of any type blade set) will hold the engine back to the desired engine rpm, then adding an additional blade will have deleterious effects on performance and will be moving backwards where propeller efficiency is concerned. Conversely, If the given blade count will NOT govern the engine at the desired rpm, then adding a blade WILL improve the propeller's efficiency and adding another blade would logistically be justified.

I am quite familiar with the Maximus blades sets (and consider them to be a fine choice), but lack enough experience with your EcoTech and your gearing to comfortably predict the point at which you would justifiably need to add a fourth blade to govern it at your intended rpm. In this regard, OneBFC, is most likely your best resource as he is both familiar and experienced with those specific parameters.
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Re: ECOTEC 2.0 LTG SWAP

Post by FISHSTICKER »

Took some measurements on my two boats.

Dragonfly....100hp, 73" narrow 3 blade I think making about 550 lb of thrust. 82" wide at the bottom and about 13' long

Prop is about 3" inside the hull. Thrust center line is 46" above the bottom of the boat, You can not position weight to make it porpoise, fun to drive super responsive.

15'x7 Robicheaux.........425 hp, wide 3 blade old water walker 79" diameter. Very round chine (like the new 12').

About 7" of blade in the hull, and 55.5" from center line of thrust to bottom of boat. I have measured this setup and the centerline of thrust is parallell with the bottom of the boat. I have not tried to make any thrust trim adjustments (raising or lower the motor.....). Using the trim tab to cruise is a must or it will porpoise your ass out the seat.

Thinking about the above input from you guys I am considering the following setup.

76" maximus (3 blade) (i can go as wide as I want, boat is actually 88" wide at the top of the transom)
49" from center line of thrust to bottom of the boat
9" of prop in the boat. (measured at the center of boat....transom here is 20" tall"

When Andrew calls me back I'll get his input.

Thanks for the discussion. Very informative.

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Re: ECOTEC 2.0 LTG SWAP

Post by FISHSTICKER »

Weighed the boat. Dead on 500# with poly.
Image

Subtract #9 for shackles and other rigging.

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Re: ECOTEC 2.0 LTG SWAP

Post by FISHSTICKER »

Had a conversation with Andrew at Water Walker about a prop today. We decided on a 76” Maximus 3 blade. Should get it in a few weeks. I’m going to run it 11” deep in the hull.

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Re: ECOTEC 2.0 LTG SWAP

Post by FISHSTICKER »

Making my list of parts I need to order.... rudders with accessories, seats, steering cable and the misc parts that go with all this stuff. Considering the cost for shipping I'm thinking it would be best to order everything from one vendor like Classic Airboats. I have never dealt with them do they get the Southern Airboat thumbs up? Any other recommendations for a one stop shop for these parts?

And happy New Year to everyone!

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Re: ECOTEC 2.0 LTG SWAP

Post by Gladesman06 »

IMO you would be better off with using Aumitech, they are good priced and easy to deal with. Most any big Airboat company can be a one stop shop like Hamant airboats, Diamondback airboats, GTO airboats, Floral City airboats, etc but my go to company is Alumitech airboats. FYI Panther and Classic airboats are the same company.

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Re: ECOTEC 2.0 LTG SWAP

Post by Ribcracker »

Same here for the most part. They always treat me well. Question>>>> when ordering a new cage for an airboat, should a flag holder be installed.? noticed yesterday morning when I finally got mine to the river that there was no holder. thought that for the amount of money I gave up to those people at panther that the least they could have done was installed a flag holder. Just about Par for that outfit though.

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Re: ECOTEC 2.0 LTG SWAP

Post by FISHSTICKER »

Pricing seems to be fairly consistent between them when you look at the totals for what I need. I think I'm going to go with Diamondback due to recommendations on their rudders.

Thanks.

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Re: ECOTEC 2.0 LTG SWAP

Post by FISHSTICKER »

New tradition. FISHSTICKER FRIDAY.
Image
No trick photo. Monster lobster picked off a rig in West Delta block.

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Slidin Gator
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Re: ECOTEC 2.0 LTG SWAP

Post by Slidin Gator »

FISHSTICKER wrote:
Fri Jan 03, 2020 3:07 pm
New tradition. FISHSTICKER FRIDAY.
sombitch :bom:
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: ECOTEC 2.0 LTG SWAP

Post by SWAMPHUNTER45 »

Biggest I've ever seen !

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Re: ECOTEC 2.0 LTG SWAP

Post by FISHSTICKER »

He was a monster 9 or 11 pounds I can’t remember.

Tig machine will be back tomorrow. Prop will be here in a few weeks. Placed my order with Diamondback. My plan is to build the engine stand to get the motor in the boat so I can test it Under load

Problems I still have.
Alternator will not charge. Could be a tune issue or wiring issue. I took the alternator to the parts store and it tested bad. Purchased a new one but the new one won’t charge either. Maybe I can get an old school 1 wire alternator fitted with a 5 grove pulley and just make a custom bracket if I can’t get it figured out. This alternator apparently requires a signal from the PCM to charge. Anyone have a recommendation for a custom alternator shop?

Motor idles real smooth when cold. It begins to idle bad after it warms up. The guy that put my harness together and put the tune in the PCM has been very helpful but tuning is not what he does. He builds standalone harnesses. So I will be looking for a tuner to help me get it dialed in. I have HPTunes so we could do it remotely.

I’v been making my way around HPTUNERS and while it’s intimidating I’m starting to figure things out. I now know the difference between MAF tuning and MAP/ speed density tuning and have a basic understanding of what they are. I certainly don’t feel comfortable enough to start making fueling changes but I do have an understanding of what it all means. If you have a tuner recommendation I’m interested.

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Re: ECOTEC 2.0 LTG SWAP

Post by FISHSTICKER »

This is what happens when you take your buddy to your favorite fishing hole :(
Image

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Re: ECOTEC 2.0 LTG SWAP

Post by SWAMPHUNTER45 »

Biggest cobia I have ever seen you got the hot spots. If you line shafted that it would take you for a serious ride I suspect if it was not a fatal hit.

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Re: ECOTEC 2.0 LTG SWAP

Post by FISHSTICKER »

All we can do is line shaft due to the conditions. Poor vis, sometimes 200’ to 500’ or thousands of feet of water depth out of the mouth of the river. You have to be willing to fight everything you shoot. This Cobia was hell bent on killing my boy Dwayne. When I got to them they were both wrapped in the grating on the bottom. We use 5/32 stainless cable on our guns because nothing else will work on the rigs. Had to break out the cable cutters.

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Re: ECOTEC 2.0 LTG SWAP

Post by FISHSTICKER »

Ok, spoke to some alternator shops. Found one that says he can replaced the voltage regulator with a self exciting one. Going see him tomorrow. I’ll report back.

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