Rocking boat

[dtarules]

I have found I can go faster if I trim up my motor but sometimes it causes the boat to rock from front to back. If I trim down the rocking stops. What makes the boat rock and how can I stop it and keep the speed?

Thanks, Drew

[willfish4food]

Like porpoising? Sounds like you have he mtor trimmed up to much for the speed you are going.

[dtarules]

Yeah it is like porpoising. I can go 31 mph with the trim all most all the way down. If trim up about half way i can go about 36 mph. I am trying to figure out how to get that last few mphs with out the rock.

[willfish4food]

Sounds like your motor is trimmed up too much. If your boat doesnot have enough lift it like this :the prop digs in and pushes the bow up then the prop get to close to the top of water and the weight of the bow pushes the bow back down and the cycle starts again. Porposing

[dtarules]

would a jack plate or hydrofoil help?

[Rudeman]

Are you running in the optimum RPM range? The figure is different from one motor to the next. Check with your dealer for the figure.

Most instances of porpoising are due to insufficient power to support the amount of trim.

If you are able to turn your prop at the optimum RPM at wide open throttle then it may be that you just need to not trim up as much.