Pontoon Boat & Deck Boat Forum

This could be just cause I am ignorant to pontoons. Which I am actually hoping.

I have had several boats...my last was a 1998 Skeeter zx185 with a 150 Yamaha vmax. So I am not completely new to boats....just pontoons.

So my issue is not being to drive the pontoon at WOT unless the motor is completely trimmed down. If I trim up at all it will have cavitation...RPM's drop and everything.

I have a 2004 Fishing Barge 21' with a 50hp tracker (mercury) motor.

I also tried a different prop with a different pitch and it was even worse. I think I have an 8 pitch prop on there now, which is what it came. I then tried a 11.5 I think. I would have to double check that as well. That ended up being worse.

I ended up selling that prop to a guy and he was talking about maybe trying to trim up so the motor is a few degrees out past perpendicular. That didn't work either.

Am I just way under powered? Is that my issue or am I doing something else wrong. Any help would be greatly appreciated.

Am I just way under powered. If so, would a hydrofoil help at all. I am not really concerned about speed. But the cavitation is pretty common....slight turns, small wakes, etc. I just want a smooth ride. Also not sure how to find out if I have the correct prop, but I am not sure if that is the real issue or not.

Check that your cavatation plate is flush with bottom of transom well. A foil might help as it did on a toon I had a few years ago

[quote="lakerunner"]Check that your cavatation plate is flush with bottom of transom well. A foil might help as it did on a toon I had a few years ago[/quote]


Ok, I will check and put up a picture later today. Thanks.

Here is a pic.

I can't tell from the pic but do you have bolt holes left on the mount to lower the motor down one notch.

That might help. be sure to leave the bolts in the notched spot just loosen them a bit. and ease it down if there are holes available.

Now with a 50 on a 21 foot pontoon you wont get much "lift" anyway. You may just need to trim for the best speed with the load you have.

Hop this is of some use.

On my old pontoon, I kept my motor's anticavitation plate parallel to the bottom of the toons.

Pontoons are displacement hulls, and they push through the water. Trimming often does nothing to improve speed anyway. \
\
About the only way to get improved performance is sheer horsepower and/or lifting strakes to get the nosecones out of the water. And lifting strakes really need 115 hp or more.

. And lifting strakes really need 115 hp or more.[/quote]


Not really . LOL

file this under PO for personal opinion, but I think you're probably underpowered.

I don't believe that your trim and cavitation problems are a result of being under-powered.
I have a 2007 22' Party Barge w/ a 60hp Mercury (not much difference from your rig).
I can trim my motor up and increase my speed 1-2 MPH and greatly smooth out the ride.
As far as props and how your motor is mounted, I am absolutely no help.
My motor and prop are how I received them, when I bought the pontoon new.

If I trim up at all it will have cavitation...RPM's drop and everything.
I think I have an 8 pitch prop on there now, which is what it came.

I'll throw a stab at it with a couple of thoughts. I think maybe the prop is the primary problem. Pontoon boats like the larger diameter props, usually the largest available that will fit without clearance issues. Too bad you didn't include your engine rpm output at full throttle and during incidences where it was experiencing cavitation. My thought is this cavitation is essentially a full loss of traction and your little 50 is overpowering that 8n pitch prop and essentially spinning it's wheels. Your RPM's are dropping because the rev limiter is kicking in to stop engine over revving. Likely a 12x11 or possibly 12x13 prop would work well for your setup. And guessing a bit because of picture angle but to me it appears the your engine may actually need raised a couple of inches for best performance.

I just wanna say "Welcome to the forum"! No real help to offer because I'm a Tritoon guy. Sounds underpowered and underpropped, though. Bamby is right, pontoons love bigger diameter wheels behind them. And loading makes a heck of a difference. Passengers and weight in the bow will negate trimming. How's it run and trim with only you in the boat? When I did my testing with Manitou, I did it all with the average loaded weight, figuring just 4 adults, 1/2 fuel and about 200 lbs of gear. Adding 4 more passengers and another 200 lbs of gear turns a well tuned boat into an absolute slug.. Taking out everything and running solo, bouncing off the limiters and chine walking is my favorite place to run.

[quote="Bryden24shp"]I just wanna say "Welcome to the forum"! No real help to offer because I'm a Tritoon guy. Sounds underpowered and underpropped, though. Bamby is right, pontoons love bigger diameter wheels behind them. And loading makes a heck of a difference. Passengers and weight in the bow will negate trimming. How's it run and trim with only you in the boat? When I did my testing with Manitou, I did it all with the average loaded weight, figuring just 4 adults, 1/2 fuel and about 200 lbs of gear. Adding 4 more passengers and another 200 lbs of gear turns a well tuned boat into an absolute slug.. Taking out everything and running solo, bouncing off the limiters and chine walking is my favorite place to run.[/quote]

I will give that a try. Also I tried the bigger prop like stated in the original post but it seemed to have gotten worse....I am not sure why though.

[quote="Bamby"]If I trim up at all it will have cavitation...RPM's drop and everything.
I think I have an 8 pitch prop on there now, which is what it came.

I'll throw a stab at it with a couple of thoughts. I think maybe the prop is the primary problem. Pontoon boats like the larger diameter props, usually the largest available that will fit without clearance issues. Too bad you didn't include your engine rpm output at full throttle and during incidences where it was experiencing cavitation. My thought is this cavitation is essentially a full loss of traction and your little 50 is overpowering that 8n pitch prop and essentially spinning it's wheels. Your RPM's are dropping because the rev limiter is kicking in to stop engine over revving. Likely a 12x11 or possibly 12x13 prop would work well for your setup. And guessing a bit because of picture angle but to me it appears the your engine may actually need raised a couple of inches for best performance.[/quote]

The RPM's were at about 5500 and dropped to about 4800 I believe. This was a couple months ago so I am not 100% of the actual RPM's Also I tried the bigger prop and it seemed to have done worse so that is why I ended up selling it. Also the motor is lowered all the way down right now. I think it can be raised a couple more times....but it can't be lowered. How could the motor being too low cause cavitation?

[quote="RcgTexas"]I can't tell from the pic but do you have bolt holes left on the mount to lower the motor down one notch.

That might help. be sure to leave the bolts in the notched spot just loosen them a bit. and ease it down if there are holes available.

Now with a 50 on a 21 foot pontoon you wont get much "lift" anyway. You may just need to trim for the best speed with the load you have.

Hop this is of some use.[/quote]

No, I can't lower it any further....only can go up.

Could this missing piece be part of the issue? Also i included another view of the rear.

On more thing....would a hydrofoil be worth trying out?