5250 vs 5,000

Airboat propeller discussion.
Basin_Runner355
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5250 vs 5,000

Postby Basin_Runner355 » Tue Aug 22, 2017 7:41 am

I have a zz4 355 on a 14 ft diamond back 2:1 belt reduction with a brand new 2 blade water walker falcons was wondering if I would see a. Noticeable gain from from 5250 to 5,000 I have them set perfect to no vibration through out all rpms don't wanna mess with it if I won't gain a noticeable amount of push on the ground
14ft diamond back zz4 355sbc 2:1 belt drive reduction with a 78 water walker falcons pitched at 5200

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kwanjangnihm
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Re: 5250 vs 5,000

Postby kwanjangnihm » Tue Aug 22, 2017 8:08 am

355 hp at 5,250 rpm and 405 ft./lbs. of torque at 3,500 rpm

5250 / 2 = 2625
5000 / 2 = 2500

2 Blade Falcon Series: Optimized for 2450 propeller RPM. Develops over 3.8 pounds thrust per available HP.
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Basin_Runner355
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Re: 5250 vs 5,000

Postby Basin_Runner355 » Tue Aug 22, 2017 8:52 am

I know the math but just don't know if 100 rpm
At the prop is gonna make a big difference I've had this boat for not even a year I'm on my third set of blades I'm tired of pitching props lol I've pitched props on this boat at least 10 times I've been fine tuning evey aspect of this boat to get the most I can so I won't have to open up the. Motor

Some ppl swear by 4900 others tell me to turn upwards of 5400
14ft diamond back zz4 355sbc 2:1 belt drive reduction with a 78 water walker falcons pitched at 5200

One Eyed Gator
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Re: 5250 vs 5,000

Postby One Eyed Gator » Tue Aug 22, 2017 12:51 pm

To me there is no set rpm for best performance, it depend on your setup. I always just take a day and play with the pitch setting till a find the sweet spot for my current combination and the conditions I run.

With that said I ran a 2:1 on a stock 5.3 (maybe 285-300hp) just never seemed right with a 2 blade 81.5" R. Sweet spot for me was right at 5050. It ran better with a short 3 blade. Two blade it seems like it was always falling off play unless you were on the throttle. 3 blade never felt that way.
I tried Falcons, Maximus (were short), super snapper, H blades (3 bld), R blades 2 and 3 bld setups.

Boat is a 14x7-6 alumitec with SS rigging.

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Re: 5250 vs 5,000

Postby scottyroll » Tue Aug 22, 2017 12:53 pm

I personally think that it makes no sense for the average guy with a 2/1 or 2.37/1 to go over the 5,250 number. I was happy running my setup there and would sometimes choke it down to 4,900 if I was just going to be cruising for the weekend. Just change it up when you some time and see if it's worth it.
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Basin_Runner355
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Re: 5250 vs 5,000

Postby Basin_Runner355 » Tue Aug 22, 2017 1:41 pm

Just sucks cause I need both I have a long ride in deep water to get to my camp and then4,900 would be nice on the cruise but onnce I get there I need the snap of the higher rpms to get me out a bind
14ft diamond back zz4 355sbc 2:1 belt drive reduction with a 78 water walker falcons pitched at 5200

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Deano
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Re: 5250 vs 5,000

Postby Deano » Tue Aug 22, 2017 3:01 pm

It has been some time since I've acquired a new set of Falcons, but presuming they have not changed, I can confidently tell you that those blades will produce more thrust with more, rather than with less pitch. With your belt ratio, the blades are already turning beyond where they were designed to. Since you are already over-spinning them, taking out pitch to turn more RPMs, would be a decidedly unproductive endeavor from a prop efficiency standpoint. More pitch is more push, as long as you can still turn it.

If everything is as you like AND Andrew confirms 2500 RPMs is OK to turn, I'd see no reason to get a heartburn about it.

If you decide you want/need to change it, adding pitch and running <= 4900 is the far more logical move to make for the reasons stated above, unless your engine simply is completely lacking the grunt to do so.
Basin_Runner355 wrote:. . . Some ppl swear by 4900 others tell me to turn upwards of 5400

Given the option, I may well pitch them more than 'Some ppl', but would never decrease pitch in order to exceed the design spec.
I would not advise anyone to over spin a new wide blade prop 250 rpms faster than manufacturer specs. Time has already proven this tact to be largely unproductive and sure as hell will not increase the any pre-existing safety margin.

Realistically, by the sound of your last post, you would likely do better with a 2.3 ratio. Your 2:1 would be viewed by some folks as a big block ratio. Still . . . you might be surprised to find that increased thrust will substitute for the 'snap' you perceive you need. If you truly need snap, wide chord blades is not the best place to start.

In any case, there is not more thrust to be gained by DEcreasing pitch, unless you are adding a blade(s) at the same time.
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but it is not the path to knowledge; it has no place in the endeavor of science."
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One Eyed Gator
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Re: 5250 vs 5,000

Postby One Eyed Gator » Tue Aug 22, 2017 4:10 pm

I know I changed to a 2.68 ratio and went to a 79" 3 blade R and my boat performs much better. I think it would have been better with a 2.55 but I got the deal on a 2.68. Still the same old stock 5.3(BTW motor had 113K and now has over 400hrs between 2 boats). Now my buddy LSmatt Ran a 5.3 with a 2:1 and a 76" 3 blade, his boat ran great with the shorter 3 blade setup.

Basin_Runner355
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Re: 5250 vs 5,000

Postby Basin_Runner355 » Wed Aug 23, 2017 5:37 am

The guys around hear swear up and down that the faster you spin the the more push you get because they "tested it with a scale doing dead pushes on the trailer. I would like to go to a 2.3 reduction but just to expensive right now I'm just trying to get it to do the best it can and I've have talked with Andrew. When I got the blades he said it wouldn't hurt to turn them at 5200 but he tells me I they push better at around 4,900.
14ft diamond back zz4 355sbc 2:1 belt drive reduction with a 78 water walker falcons pitched at 5200

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Re: 5250 vs 5,000

Postby Sniper » Wed Aug 23, 2017 6:33 am

When I had my first boat I had a ZZ4 on it and RPM made a huge difference in power I have run all my boats around 5600 rpm WOT my new boat with the LSA on it I am running at 5400 the super charger made up for the RPM, Water Thunder got me to running more RPM and as usual he was right made a big difference in power
Last edited by Sniper on Thu Aug 24, 2017 8:32 am, edited 1 time in total.
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Basin_Runner355
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Re: 5250 vs 5,000

Postby Basin_Runner355 » Wed Aug 23, 2017 9:04 am

RPS!??!
14ft diamond back zz4 355sbc 2:1 belt drive reduction with a 78 water walker falcons pitched at 5200

Swamp Thang
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Re: 5250 vs 5,000

Postby Swamp Thang » Wed Aug 23, 2017 9:29 pm

Basin_Runner355 wrote:RPS!??!

I think he meant to say RPMS

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Re: 5250 vs 5,000

Postby mojoe » Thu Aug 24, 2017 7:16 am

Swamp Thang wrote:
Basin_Runner355 wrote:RPS!??!

I think he meant to say RPMS


RPMS (R--P.M.S.): revolutions on a motor that is running like a bitch!
Airboating is like marriage: There are unlimited ways a person can be right, and somehow still be wrong at the same time!!

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kwanjangnihm
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Re: 5250 vs 5,000

Postby kwanjangnihm » Thu Aug 24, 2017 7:43 am

Sniper wrote: RPS made a huge difference in power - Water Thunder got me to running more and as usual he was right made a big difference in power

Waterthunder deals in revolutions per second not minutes! :toothy7:
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Re: 5250 vs 5,000

Postby Sniper » Thu Aug 24, 2017 8:34 am

one little typo and you guys have a field day lol
Sniper You can run but why die tired, If you heard my shot you were not the target
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Re: 5250 vs 5,000

Postby Prototype » Fri Aug 25, 2017 9:16 pm

Basin,
Your going to pay for that need in some fashion! I think I read down this correctly,,, when you said you can pitch a prop at ease? Reading through all the stuff your either going to carry a torque wrench and paint stick, or your not going to upgrade without funds?
I'd say the earlier is a better bet if your camp is substantially far? I'd think your talking at least two hours at speed on the water to warrant such a task?

If your brand new Falcons work for you that's great! Get yourself some weather proof stickers or scribe to mark the 2 needs. It's entirely possible you could do both cruise and hunt with your present setup, with a torque wrench?
If you really don't like tweaking it you could also over power and over drive the boat? Most do just because they like the safety factor.
I will say one thing though that all can agree with,,, That additional 250 rpm you presently have should only be discarded for cruise savings.
I wouldn't touch it unless your talking hours of cruise savings on a regular basis?

Basin_Runner355
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Re: 5250 vs 5,000

Postby Basin_Runner355 » Sun Oct 01, 2017 8:14 pm

Just a update I had a vibriatin so I repitched one of my blades were off so I set them straight and it turns a hair over 5,000 and this weekend i had the most load I've ever had in the boat 3 ppl dog. 65 qt yetti full tank 10 extra gallons of gas for generators a push mower guns and our clothes took a Lil bit to get on step in deep water I could stay on step at and cruise at 3,800 and when I hit the shallows I could cruise at 2800-3000 I think Ima leave them where they are and I dint have to use my spray tank all weekend
14ft diamond back zz4 355sbc 2:1 belt drive reduction with a 78 water walker falcons pitched at 5200

Basin_Runner355
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Re: 5250 vs 5,000

Postby Basin_Runner355 » Sun Oct 01, 2017 8:16 pm

45 min boat ride one way rode around the lease a good bit and came back burnt less than a 1/2 tank im happy with that
14ft diamond back zz4 355sbc 2:1 belt drive reduction with a 78 water walker falcons pitched at 5200

SWAMPHUNTER45
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Re: 5250 vs 5,000

Postby SWAMPHUNTER45 » Sun Oct 01, 2017 10:57 pm

Leave it alone that is probably a good setting based on your reported results.


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