2nd opinions on prop selection

[joesnuffy]

I am running a 40hp Yamaha 2 stroke on my pontoon boat is only has 2 pontoons it is about 19.5ft. Top speed is about 18-19mph with me and the wife and that’s not all the way full throttle but close. When we start adding people to the boat it slows it way down. I have had about 7 people on it at once and the 40hp works like crazy just to go fast enough for a breeze but its a good time. Normally its just me and the wife so we like the 40hp its also easy on fuel. Don’t know if this helps but I do believe the hull drag concept I could go with a much larger engine but I don’t believe I would get much more speed except for when I got a lot of folks it would come in handy.

Joe

[fisherman6]

As I said, I’m no expert in hydrodynamics by any means. I have 3 14′ aluminum boats powered by tiller controlled outboards and a traditional 2-toon pontoon boat with the small diameter toons. The toons are 19’11" long and the deck is 16′. I have a 1976 Johnson 55hp on it. When I bought the motor it had a 17P prop on it and with that prop it would run along at 15-16mph and top other at maybe 4000rpm. It was lugging with that prop. I changed to a 13P prop with a slightly larger diameter and it was like a whole different boat. Motor runs at about 5000 rpm at WOT amd the boat moves along at about 20mph. Most of the time this boat is running at about 50-75% throttle and about 10-12 mph. I’m on the 3rd or 4th trim pin hole out where the AV plate is approx level with the water line when the boat is in the water. This seems.to be the ideal setting for my boat. That’s with me, my wife and 7 year old daughter on board. More people and it gets slower pretty quick. The tri-toon may be a bit different. I have no personal experience with tri-toons, but I know they often come equipped with much larger motors than traditional 2 tube pontoons. For whatever that is worth.

I know there is a lot different and more turbulent water flow under a pontoon boat hull than a traditional planing hull. I was not aware that major boat builders were building tri toons with the center tube lower on the water than the two outer ones. I’m not sure why they are doing that. My guess is that with the much higher power capability of the tri toon, the lower center tube would act more like a center keel and allow for more precipe steering with a large motor pushing the boat at high speed (40+ mph). With the boat moving at a speed that is barely planing the outer tubes (18-22 mph) the lower center tube seems like it is simply adding drag to the hull. The added turbulence created by the center tube that requires the deflector to keep water out of the boat has to be slowing it down. I’m also imagining that turbulence is making the prop cavitate when it is trimmed up. These are only theories from the seat of my pants and my limited experience. I could just as easily be "all wet" so to speak.

For what it’s worth, I also have a small pontoon I built out of an old pedal boat that I use on my pond. It has 8′ long toons and a 6′ deck. With a 4hp tiller outboard on it, I’m very limited on how quickly I can turn without prop cavitation. The turbulence created by the tubes in a turn really messes with the water flow to the prop. I have to back the throttle off so it doesn’t pull air from the surface into the prop thru the eddys. None of that is present with my planing hull boats. Pontoon hulls seem to have a different set of rules. Just my 0.02.
-Ben

OldJohnnyRude on YouTube

[jerry-ahrens]

The larger diameter center pontoon will cause the boat to drive more like a V bottom would. On turns, it will perform much better. Bennington is one manufacturer that does this. Check out the Quicksilver Nemesis Pontoon prop. I always turn to Quicksilver props to solve many performance problems on various boats I’ve worked on. https://www.quicksilver-products.com/en … ropellers/

[dan-in-tn]

Just some of the latest things going on below the waterline on pontoon boats. Now what’s going on above the water (engine wise & expense) may seem ridiculous to many, but that’s a whole different story!

https://m.youtube.com/watch?v=OGhrete64 … vk08n-ro8B

Dan in TN

[dan-in-tn]

And then the absurd! I think this is in Jerry’s back yard.

https://www.youtube.com/watch?v=j136TTyG_E8

Just your 114mph pontoon ride. Guess they overcame that displacement theory. Weird seeing all that air under that boat.

Dan in TN

[johnyrude200]

I guess I need to add 2 more engines to my boat…

I may try a 70hp next season, but need to evaluate my structural engineering before heading down that road. More worried about the outer tube tie-ins/welds and c-channel cross members than anything else.

The center tube came off a grumman 20′ that was rated for 70hp. The outer tubes came off a small pontoon from the early 80’s that I suspect was probably rated for no more than 25-30hp (no rating plate). So the tie-ins are the weak part of their design.

[rudderless]

https://youtu.be/NNPxRvdAusA

You need this motor…

[johnyrude200]

The camera guy had too many wobbly pops prior to filming.

[jerry-ahrens]

Yea Dan, that’s from the Lake Rescue Shootout. Actually it starts tomorrow and goes all weekend. Lot’s of big boats coming down to Lake of the Ozarks this weekend. They even have a bass boat shootout! You do not want to be out there when the event is over on Sundy though…. unless your’e in a 40 ft. or bigger boat. I made that mistake once, years ago. Thought I was literally gonna be ran over and killed. I know a delivery driver that has been delivering bagged ice to businesses around the lake. He said it’s insane how much ice lake area businesses have ordered for this weekend.
We had some fatalities in 2014, when a guy flipped a big cat, and it went end over end several times before coming to a rest. https://www.youtube.com/watch?v=3ubukX0ZgtI

[fisherman6]

Jerry, just wondering want kind of power the Bennington tri toons with the lower center tube are typically equipped with. I can certainly see the advantage of this concept if the hull is being pushed fast enough. It just seems to me, like a planing V-hull, until you push it fast enough to realize the handling advantage, it’s just more drag. Maybe I’m wrong.
-Ben

OldJohnnyRude on YouTube

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