porpoising ?

I have a 14ft Grumman aluminum v bottom that weighs between 150-200lb. I had a 9.8 merc on it, but decided to upgrade. I put a 20 Hp Tohatsu on it, which is probably 40 lbs heavier, and im living a nightmare. The boat is rated for 25hp. I can barely go over idle without the boat feeling like its going to flip on top of me. I am no lightweight (285Lbs), so Im pretty sure its a weight issue with the new motor. Anyways, with my wife in the front (110 lbs) its still not bearable. when I do get the guts to crank on it a little, it planes down, but still bounces all over the place and I have no control. Is there anything I can do to help? or am I going to have to put a few 80 lb bags of concrete in the bow? the engine is pull start by the way, so I don't carry any batteries, just a 3 gal fuel tank and a few fishing rods. another question I have is, would the 20 hp be underpowered for a 500 lb 16 ft boat?

Re: porpoising ?

Try lowering the tilt pin. Lessen the angle of the motor.

Re: porpoising ?

cr2k said:

Try lowering the tilt pin. Lessen the angle of the motor.

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the tilt pin is as low as it goes. Do the hydrofoil fins work, or just a waste of $?

Re: porpoising ?

I would not Buy a hydrafoil Yet. how many seats in the boat? The wife may need to move to the center seat. It is all about weight distribution, on smaller light weight boats. Sometimes the is difference wether, the passenger is facing foward, or towards the back of the boat.

Re: porpoising ?

there are 3 seats. me in the back and she usually sits In the front. I thought with her in the front it would help keep the bow down, but next time ill try her in the middle seat. Im concerned when im by myself, as that's mostly the case. maybe its time to step up to a 16 and put the 20 on that. a wider boat should be more stable, and I could always use the extra room.

Re: porpoising ?

Hydrofoil fins are better than sliced bread. Every boat should have one. But that won't help you. Sounds like you are plain and simple overloaded. You need a bigger boat.

Re: porpoising ?

IMO, Hydrofoil fins puts too much "up lift" stress on the motor. Since motor is connected to transom, the transom endures the stress. And, this stress is focused in a central area - where the motor is bolted on. Suggest looking at Smart tabs. Some brands of Tabs are low cost "screw on" and leave them. Other brands are wired to a central panel - that allow individual movement / angle of each tab. Since Tabs are screwed on the lower hull and on the outside sides of the boat, the "up lift" stress pressure is distributed on the outside of the boat's corners. Thus, creating much better stability on sharp corners as well. And, less flip/flop from side to side - like the Hydrofoil fins centre lift position. If wondering, I have Smart Tab SX on my boat and love them. Install them, leave them and they work great.