Tritoon - Prop and Motor Height

[Southerntoon]

Hello

Still working on Motor Height and Prop Size. 24FT Tritoon - Honda 200 - 4 Blade 14.25 x 17 Prop - Manual Jack Plate
I can not seem to get to the suggested rpm range of 5500-6000 rpms

I keep my toon in a wet slip. I took it out a few weeks back and cleaned the toons and had the motor serviced and checked. With about 550 lbs of people the boat would run about 40-42 mph at 5100-5200 rpms. Jack Plate set about 1/3 of the way up in adjustment - can trim only about 25% -30% before it seems to start to cavitate and mph goes down.

A week ago with about 3 weeks of sitting in the slip - we took it out - double the weight to about 1100lbs of people and it would only run about 25 mph at 4800-5000 rpms. So I dropped 15 mph and about 300 rpm.

Yesterday I raised the motor up by adjusting the Jackplate about 2/3 of the way up. It seem to pick up a few hundred rpms and about 2 mph to 27 mph with about the same 1100 lbs of people etc. Trimming now only about 20% up on the gauge and the motor seemed to be cavitating above 5200 rpm and mph would start going down. Not sure how much trim most have to play with on a tritoon if the motor height is correct?

Trying to get motor height right before new prop - alot of people have suggested moving to a 3 blade ?? instead of a 4 blade at anywhere from a 15, 17 or 19 pitch. What about diameter of prop in relation to pitch??

Here are a few pictures of my motor running wot - let me know what you think about height. Any advice or comments will greatly appreciated !! [img]C:\Users\Sereena\Desktop\Honda%20Motor[/img]

[Bryden24shp]

4 bladed props generally are stern raising props. Thats probably your cavitation problem. If you pop on a 3 blade, you'll see a noticable difference. I can't see the cav plate on the surface. I would stick on a 3 blade and see where you are at. PM me again if needed...

[Bamaman]

I agree with Bryan about going to a high quality 3 blade prop, and you might want to reset your original engine height for comparison/baseline. You didn't start off that far from your expected maximum mph.

Pontoon/tritoons are different animals when you're trying to set'em up. There seems to be a point of no return where you get to 30 mph on a 2 toon boat and 40 mph on a 3 toon or straked hulls--where any more mph takes sheer horsepower or a perfect engine/propeller setup combination.

And since there's a wide variance in boat weights, rules change between different brands/models of boats. I have an old Starcraft pontoon boat with a Yamaha 115 hp 2 stroke, and it's quick to ventilate if I get too many people sitting up front. Nothing I've ever done has stopped it, so I've had to sometimes just ask people to sit in the back.

I've always read at moderate speeds, you should be able to easily see your anticavitation plate through the water spray. My Bennington's setup properly, and I still cannot see the plate when running. Nix that.

Good luck to you.

[Southerntoon]

OK - we do not have a descent prop shop around here that has a nice selection to try before buying . So what diameter and pitch on a 3 blade do you guys think will work best.

I really feel like this boat should run 45 mph lite and around 35 mph loaded down. I keep seeing post with people posting that they have a 22FT pontoon with a 150 running 35 -38mph. I would think going from a 4yl to 6cyl on a tritoon it should be able to get up a roll

Thanks for the insight!

[cwag911]

I would say a 15 x 15 or 14 3/4 x 16 Enertia would do it.

[Southerntoon]

What causes prop slip? I used an online calculator and my prop slip is around 40% and that seems to point to something being wrong?