Pontoon speed help

[dj0443]

I have a 24' smokercraft. I just added a 3rd toon with built in transom and lifting strakes.Put a 94 115 johnson motor.Have tried a 14x11 and a 14x17 prop Got plenty of hole shot but only getting about 21mph at 6000 rpm.I was getting more speed out of the 70 hp with the pwg .Any help would be appricated.

 

[Kainon]

Re: Pontoon speed help

What is the WOT Rating for the engine ?

If the RPMs are the same with either prop, I think your still under propped.

You may just be topping out the engine, see if you can try a bigger prop, see if the RPMS start coming down..

 

[Silvertip]

Re: Pontoon speed help

The 17P prop shows 56% slip. The 11P shows 32% slip. Either the tach is wrong or adding the third pontoon has created a terrible turbulence problem and the prop can't get a grip. My thoughts are trying to make a speedster out of a pontoon is like putting lipstick on a pig. Why bother. That's probably not what you wanted to hear but engines on a pontoon run in very turbulent water and ventilation can be an issue. The third tube can make this problem worse. The only solution may be to modify the engine pod or add a bracket that moves the engine back to get the prop in less turbulent water. Have someone who knows their way around props follow you and I'm almost positive they will tell you the prop is not getting a bite. Try a four blade pontoon specific prop. This prop will have big rounded blades with lots of blade area. If lifting strakes have been added on only the outsides of the pontoons, those would not have any affect on ventilation.

 

[lmuss53]

Re: Pontoon speed help

I've seen them recommended here and on other forums in several posts, can anyone point me to somewhere where I can buy a "pontoon specific", "elephant eared" or "extra cupped" prop? I believe these critters are a pontoon boat forum myth. I've seen props described as "elephant eared" for small, under 20HP, merc outboards that are no longer available, and I have a Michigan Wheel that had "exrta cup" somewhere in the description but is out of production and has been for 20 years. I haven't been able to find a new or used prop with any of these terms attached to it anywhere on line or in shops.

To answer the OP's question, I would do as suggested, see if you can borrow a 19 or 21p prop and see what it does. If you try the 19 or 21 and still get that 6000 rpm then you do need to get the motor down, or back into some smoother water. Most 115hp, 21 or 22 foot boat owners that post about props are using 15 to 17P props. I hope whoever just built you a center tube with a built in transom thought about the fact that you were trying to get a little more speed out of your boat when you had it built.

I just added a 10 foot long 3rd tube and a 90hp Johnny to my 20 footer and I'm getting 25mph by GPS at WOT with an old Michigan Wheel 15P. The tach isn't working so I'm going tomorrow morning to get that fixed. I was getting 27mph with an OMC 17 but until I get the tach working I don't want to take any chances on lugging the motor down.

 

[Silvertip]

Re: Pontoon speed help

Mercury made a pontoon prop in 14x9 and a few other pitches. It is not difficult to identify a prop that will work on a pontoon. Just look for the big rounded blades. The more blade area the better.

 

[Jeep Man]

Re: Pontoon speed help

I have a 14x11 and a 14x9 Bigfoot props but they are for a Merc. I would think they are available for jonnyrudes as well.

 

[Jeep Man]

Re: Pontoon speed help

The 17P prop shows 56% slip. The 11P shows 32% slip. Either the tach is wrong or adding the third pontoon has created a terrible turbulence problem and the prop can't get a grip. My thoughts are trying to make a speedster out of a pontoon is like putting lipstick on a pig. Why bother. That's probably not what you wanted to hear but engines on a pontoon run in very turbulent water and ventilation can be an issue. The third tube can make this problem worse. The only solution may be to modify the engine pod or add a bracket that moves the engine back to get the prop in less turbulent water. Have someone who knows their way around props follow you and I'm almost positive they will tell you the prop is not getting a bite. Try a four blade pontoon specific prop. This prop will have big rounded blades with lots of blade area. If lifting strakes have been added on only the outsides of the pontoons, those would not have any affect on ventilation.

Not to hijack the thread, Silvertip, but you have recommended the 4 blade prop often. Would I see improvement by changing out my 14x11 on my 60 hp Bigfoot for a 4 blade, and if so, what pitch would be suitable?

 

[AquaPatioMD]

Re: Pontoon speed help

I have a 24ft Aqua patio with 2 tunes and had a 115 on it and was doing 21 at WOT and 5400 rpm with a merc 115 2 stroke, had a 14x21 which was crazy, then did carb rebuild and went to a 14x13/ scraped tunes and got almost 27, They told me that the 3rd tune is more drag. My neighbor has the 3rd tune and a 150 Yamaha and only does 27, I am getting a 150 optimax and am hoping for 35, might be dreaming but its a goal!

Good luck with your speed.

 

[Silvertip]

Re: Pontoon speed help

Switching from three to four blades, or four to three, aluminum to stainless, different manufacturers but same pitch is nearly impossible to predict what the outcome will be. Prop selection when you get down to the "fine tuning" point is strictly trial and error. I have no idea what the speed and rpm numbers are your 60 BigFoot with a 14x11 and therefore cannot predict what you need. On workboats, barges and pontoons, four blade props generally provide more push and work better for reverse manuevers. If the 14x11 puts the engine at or very near the top fo the engine manufacturers recommended WOT rpm band with an average load, you have an optimum setup for that prop and load. The same pitch in a four blade, same material, from the same manufacturer would likely increase hole-shot (sort of a joke when talking about a pontoon) but top end might drop a tad or it might increase a tad. Engine rpm might decrease a tad or it might increase a tad although this is not very likely. If you have to buy a prop for an engine that doesn't have one and it is for a pontoon, I recommend a four blade. I also recommend a four blade if there is evidence of prop ventilation or some other "propulsion" issue. I do not recommend a four blade if the three blade you have is performing well. There is simply no cost justification for this -- unless you have a very thick wallet and simply want to squeeze every tenth of a MPH out of the rig. That's where the impossible to predict situation arises and trial and error becomes necessary.

 

[lmuss53]

Re: Pontoon speed help

Something to consider if you want to try a 4 blade is the ComProp brand of composite props available at Bass Pro. I used one on a 75 Merc on a 20 foot Fisher pontoon with real good results for about 4 or 5 years. For about $75 they are a good back up or even primary prop.


http://comprop.com/

 

[Jeep Man]

Re: Pontoon speed help

Switching from three to four blades, or four to three, aluminum to stainless, different manufacturers but same pitch is nearly impossible to predict what the outcome will be. Prop selection when you get down to the "fine tuning" point is strictly trial and error. I have no idea what the speed and rpm numbers are your 60 BigFoot with a 14x11 and therefore cannot predict what you need. On workboats, barges and pontoons, four blade props generally provide more push and work better for reverse manuevers. If the 14x11 puts the engine at or very near the top fo the engine manufacturers recommended WOT rpm band with an average load, you have an optimum setup for that prop and load. The same pitch in a four blade, same material, from the same manufacturer would likely increase hole-shot (sort of a joke when talking about a pontoon) but top end might drop a tad or it might increase a tad. Engine rpm might decrease a tad or it might increase a tad although this is not very likely. If you have to buy a prop for an engine that doesn't have one and it is for a pontoon, I recommend a four blade. I also recommend a four blade if there is evidence of prop ventilation or some other "propulsion" issue. I do not recommend a four blade if the three blade you have is performing well. There is simply no cost justification for this -- unless you have a very thick wallet and simply want to squeeze every tenth of a MPH out of the rig. That's where the impossible to predict situation arises and trial and error becomes necessary.

Thanks for the reply. That answers my question

 

[hopscotch840]

Re: Pontoon speed help

I've seen them recommended here and on other forums in several posts, can anyone point me to somewhere where I can buy a "pontoon specific", "elephant eared" or "extra cupped" prop? I believe these critters are a pontoon boat forum myth.

OMC Hydrus prop # 775713 pontoon and workboat specific prop is not a "Pontoon Boat Forum Myth" It is "extra cupped" and does work.

 

[rrhodes]

Re: Pontoon speed help

I posted my results last year. I would look at the turbulence issues others have mentioned. Here are my results.

2008 JC Neptoon 25' Triple tube w/ 2008 Honda BF115

Stock Solas Prop 13p
5800rpm and a top speed of about 28mph

Hustler Prop 13p
5900rpm and a top speed of 29mph

In addition to the 1MPH increase I noticed a significant increase in Hole Shot and mess cavitation in turns. With the stock prop I had a significant decrease in speed when making tight turns which made tubing boring to say the least. This time I dropped to about 26 mph in a hard turn so tubing should be more fun this year.

 

[dj0443]

Re: Pontoon speed help

What was the difference in props

 

[lmuss53]

Re: Pontoon speed help

Thanks hopscotch, I also saw a Merc Black Max "extra cup" designation on some prop descriptions since I posted my question, so I guess these critters do exist.

Are the OMC props you mentioned still available anywhere?

 

[4weekends]

Re: Pontoon speed help

I just bought a Stiletto Star II Stainless prop this week. It is supposed to be pontoon boat specific. The largest pitch for this prop is 15". Maybe this is what you are looking for.

 

[dj0443]

Re: Pontoon speed help

Please let me know how it does.