Prop?

sockeyerun

Seaman Apprentice
Joined
Apr 23, 2001
Messages
36
Howdy,Here's a challenge. Need a prop recommendation on a 18'Koffler wide bottom river sled that weighs 1600lbs loaded, and I'm restricted to 35HP(detuned 40HP Yamaha)Right now I'm running an aluminum 11 5/8x11 That was recommended to me buy a local dealer.Out of the hole is OK, the speed is 21mph.Think I should be doing better or because of the weight to HP ratio,I'm about max. Thanks
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JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: Prop?

Howdy, sockeyerun. What rpm are you turning when you get 21 mph? Actually it sounds like a pretty good top end for such a heavy rig, flat bottom or not. RPM is the key; if you are turning at the top of the operating rpm that's all you're gonna get. If you are going past top rpm try going up an inch or so on pitch. If you are not reaching operating range, come down an inch or so.<br />Good luck.<br />JB
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sockeyerun

Seaman Apprentice
Joined
Apr 23, 2001
Messages
36
Re: Prop?

OK,I now have installed a Tach.My top end RPM's are 5500,my book says 4500-5500. My top end speed(GPS)is 19-20. I really would like to get on step quicker. I did order those Pirhanna fins,waiting for them to show up.my prop now is a 11 5/8 x 11. any suggestions? Thanks
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JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: Prop?

You have the optimum prop for your current situation, Sockeyerun. When you get the hydrofoil fins installed you should notice a quicker jump to plane and you might also be able to rev past 5500 (not a good idea). Because you seem more interested in acceleration than top end, I would say stay with the prop you have and avoid revving over 5500.<br /><br />Good luck.<br />JB
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sockeyerun

Seaman Apprentice
Joined
Apr 23, 2001
Messages
36
Re: Prop?

Hey JB, I have another question. I have been considering purchasing a new 4-stroke. Due to my horsepower restriction(35)on the Kenai river up here,any motor I buy will have to be detuned to 35hp.Would I gain anything by changing from 2 to 4 stroke in performance?
 

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: Prop?

Howdy, sockeyerun. As you probably know, I recently repowered from a cross charged 105cu.in Evinrude 100 2 stroke V4 to a 80 cu. in. Suzuki EFI 4 stroke 70 on my 17' Whaler. Starting, idling, trolling, cruising are a whole new world of immediate, butter-smooth responses. Quiet as an electric, no smoke, no oil in the water, no "perfume de petroleum". Sips unleaded regular like an old woman sipping tea at a lawn party. I am still dazzled by this engine every time I go out. W.o.t. is just under 38mph @ 5800rpm, trimmed out to the edge of porpoising, which is less than 1mph slower than the V4.<br /><br />Believe it or not, the Suzuki/Evinrude 3 cylinder DF50/40 EFI is just as smooth and impressive. 50 cu. in. detuned to 35hp should be the talk of the season on the Kenai. Computer engine management and EFI make these engines the class of small/medium 4 stroke engine technology.<br /><br />Any 4 stroke in that range will shame your very good Yammy, but the Suzuki/Evinrude DF40 EFI will shame the rest.<br /><br />Have fun shopping.<br />JB
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