2.75's are they just bad designs?

[jlh3rd]

I've tried to find your specific model. Is it a tri-toon?

 

[nasdaqsam]

I've tried to find your specific model. Is it a tri-toon?

Not a full tritoon. It has the center toon that goes 3/4 of the way back.

 

[ahicks]

Update: taking a closer look at the height. I was incorrect. The boat is on a hoist so I couldn't get a good look from a level perspective. In doing so the cavitation plate is actually an inch below the bottom of the motor pod. So appears to be correct.
So thinking possibly prop issue. I called several prop sales companies and gave all the info, current performance and cavitation issues. All three independently recommended the same prop. The Blackmax XC 3blade aluminum 16x13P. The current prop is an aluminum 3 blade 15.25x15P.
This prop is apparently built specifically for pontoon boats. The wider 16" with deeper cupping helps with the cavitation pontoons experience. The 13p "should" get the RPM's into the correct operating range.

Thoughts?

Sounds good on paper!
I have 13 and 15p 3 bld props for my Honda 90 powered 24'. The 13" just launches the boat from a stop - will pull about anything up. Top rpm about 6200 (motor rated for 6k, and there is no rev limiter), top speed about 24mph, and the motor is sounding pretty busy.....

The 15" prop has a little more sedate launch, nothing like the 13", but not that bad/noticeable. It turns up about 5500 rpm, is 2 mph faster on top end, while sounding like it's not cranking it's guts out. Clearly the better prop for cruising and gas mileage.....

My point is, clearly there's a compromise. Which way YOU go is about YOUR priorities! How often are you planning on pulling anything/drag racing other boats? There is no wrong or better answer here. This call is on you....

You're already in the "correct operating range"!

 

[jlh3rd]

Not a full tritoon. It has the center toon that goes 3/4 of the way back.

ok..well...so the plate is below the motor pod but just wonder if that 3/4 center toon is causing flow issues. If it was me, Id be trying to see where the plate is in relation to the water when at speed.
Anyway.
these are my #'s on the props I've run. 24', twin tube(25"), '21 Merc 115 CT.
Dealer setup left room to drop the motor one more position if needed, and it did.
#'s show different results, same boat.

 

[nasdaqsam]

Sounds good on paper!
I have 13 and 15p 3 bld props for my Honda 90 powered 24'. The 13" just launches the boat from a stop - will pull about anything up. Top rpm about 6200 (motor rated for 6k, and there is no rev limiter), top speed about 24mph, and the motor is sounding pretty busy.....

The 15" prop has a little more sedate launch, nothing like the 13", but not that bad/noticeable. It turns up about 5500 rpm, is 2 mph faster on top end, while sounding like it's not cranking it's guts out. Clearly the better prop for cruising and gas mileage.....

My point is, clearly there's a compromise. Which way YOU go is about YOUR priorities! How often are you planning on pulling anything/drag racing other boats? There is no wrong or better answer here. This call is on you....

You're already in the "correct operating range"!

I'm looking for a good all-around prop that cavitates a little less than the current one. My days of racing pontoons was over when I sold my previous 60mph toon. lol.

Being a 150hp even at the bottom of the operating range the boat has no issue out of the hole even towing tubers. I would like to see how it would perform closer to the top end of the range though.

 

[nasdaqsam]

ok..well...so the plate is below the motor pod but just wonder if that 3/4 center toon is causing flow issues. If it was me, Id be trying to see where the plate is in relation to the water when at speed.
Anyway.
these are my #'s on the props I've run. 24', twin tube(25"), '21 Merc 115 CT.
Dealer setup left room to drop the motor one more position if needed, and it did.
#'s show different results, same boat.

Interesting numbers. One issue I have around here is that no one stocks a lot of props so testing is going to be buying them and returning them if I can even do that. The people I spoke to at the three online prop companies all felt the 16X13 Blackmax XC was what I needed. Of course, every boat is different. I'm going to check their return policy. If they do take them back it wouldn't hurt to try it.

I had a 1996 Sweetwater tritoon with a 115hp yamaha on it. It ran 32mph with just me in it. In 1996 that was a fast toon. I was determined to get a few more mph out of it so swapped out a bunch of props. None made much of a difference. I'm just hoping this does not end up being the same situation. A lot of fuss for no significant change.

 

[ahicks]

My 4 stroke experience has been you'll find this at about 500 rpm below max rated rpm. Save max rated for pulling duty....
"I would like to see how it would perform closer to the top end of the range though."

"None made much of a difference."

When talking a family pontoon boat, unless you're into splitting hairs, that's been my experience as well.....

 

[jlh3rd]

yep..good luck with that. It Just depends on your goal.
you can tweak, but that can get expensive. ahicks is right.
When I went from my 60 hp to my 115 hp, I only gained 6 mph. But I did get the tube hauling performance I wanted, but at a significant gas cost....
I tore up my 3 blade, 16x12, the 4-14x14 is on now ( the spare), and I just got a solas 3-15.5x13...this will be my absolute last one. I have a 3-16x13 and I get max 5800 with 24.4 mph.....but want to see if I get the 6000 rpm@max throttle......curious what the speed will be.
But you can see that the different props mainly trade one performance # to another.

 

[nasdaqsam]

I might have found the real issue. While boating yesterday I noticed the electrical gauge every once in a while, bumping as in it had a slight draw but only for a split second. As I watched it do this, I noticed the trim going up slightly, almost imperceptible. But after a few minutes it was raising the motor enough to cause it to cavitate. Thinking back to when it did it before when I stated trimming it down did not help. I found that when I tried to trim it down by holding the trim switch down while it was trying to raise it, it wouldn't do it. I have to bump the trim down to override the motor switch.

I had read about the switches on these motors causing the trim to go fully up but disregarded as mine wasn't doing that. Anyway, I pulled the cowling off and disconnect the trim switch. We rode for about 2 hours with no issues.

I can't say no issues. We were in some pretty heavy boat wakes and it cavitated twice, but I think that was due to just being thrown around causing it to lose bite, especially since all the passengers were sitting forward. I still have to stop the boat to get it to dig back in so I believe going to the bigger diameter prop might help a bit. I'm going to see if I can find one to try before I buy one but that might be next year as we're getting ready to close up the house for the fall and head back to Florida.

Thanks for all the assistance. Hopefully my experience helps to add to the resources on the forum.

 

[Scott Danforth]

glad you found the issue