Trying to match boat and motor combination.

[plugin' away]

Hi,i I have a 14 ft fiberglass, Winner boat that i was using an '86 25 johnson long shaft. This combination did well for two people but was insufficient for three people.(wouldn't plane) I have changed motor to a 35 hp '82 Johnson short shaft and this motor although rated at 10 hp more is less effective and doesn't even plane the boat with two people in it.
The motor seems to to opperate well but seems under too much load and won't wind out to top rpm. I have tried to ajust the trim pin and no luck. Any suggestions would be greatly appreciated. Thanks, G

 

[sheboyganjohn]

Re: Trying to match boat and motor combination.

The cavitation plate (flat area above the prop) needs to be even with the bottom of the boat. If it is above the bottom of the boat it is not getting clean water to run in. Since you took a long shaft off the boat and put a short shaft on this could very well be your problem. Only a couple of ways to fix it, first is to put the old motor back on, next, would be to find a the parts to convert it to a long shaft, or last (and worst) cut the transom down to a short shaft. If you still have the old motor try putting it back on and change the prop to a lower pitch.

 

[Bigkat650]

Re: Trying to match boat and motor combination.

It is also possible that the 35hp has the correct transom height but has the wrong prop on it. First thing would be to check the height of the cultivation plate. If it is right at the same height as the bottom of the hull, you have another issue. If that plate is higher then the bottom of the hull, that is definitely the problem. Check the height. If you need a long shaft motor, you will not be able to use the short shaft unless you modify either the boat or extend the leg on the motor, or get a different motor. 35HP should be plenty to get you on plane with.

Good Luck