short shaft vs. long shaft

[jwilkey84]

I have a 20 hp long shaft on a jonboat that is made for a short shaft. The motor seems to sound good but it will not get the 12' boat on plane! Right now, my cavitation plate is 9" below the bottom of the hull and the prop is about 13" below the bottom of the boat. I just have this motor on this boat to test it out. Do you think that with the prop that far down that it just cant get the boat on plane. You can also read about this on my other thread called " johnson 20 runs good but will not open up at full throttle" It seems as though that thread fizzled out so I am trying it from this angle.
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[Benny1963]

Re: short shaft vs. long shaft

your cavitation plate must be around 1 inch below hull or it will kill off your ability to plane and sometimes pushes water over your transom
you can get a braket on here cheap for the smaller motors
your lugging your motor with your prop that low
good luck