Re: prop cavitates
Little boats don't cavitate. You may be ventilating, which is the prop sucking air down from above. Your options are pretty limited with an I/O. You may need a prop with more pitch. Also a whale tail, or something similar may help. If you have changed the balance of the boat ALOT, that may have done it.
I bought a cheap prop on e-bay to use to limp home, it was a 13 pitch, I usually run a 19. I would ventilate from a stop, but if I added power slowly I could get up to speed without it happening.
What kind of RPM do you get WOT? Add an inch of prop pitch for every 100 RPM you are too high (above redline) with a normal load on the boat. Normal load for you.
I'd estimate you should be running a 14.5 x 21 prop, maybe 14.5 x 23. 3 blades or 4 makes a difference, stainless vs aluminum makes a difference, and mickey mouse blades vs schimitar blades too. I defer to the prop gurus on that. It is as much an art as science.
Good luck.
--Jim
