Steve W Posted July 21, 2014 Report Share Posted July 21, 2014 Yesterday I tried a 4HP Mercury standard shaft (15") outboard on my 11N. I built the boat exactly to the plans. As it sits, the OB "plate" just above the prop, sits just slightly lower than the hull. Of course the short keel aft is slightly below the plate. This motor seems to be a good match, but as soon as I turn even a little bit, the prop cavitates and sucks air, sending it revving and only biting when I run it back close to idle. I want to use this as a fishing platform when not sailing. I put my long shaft Honda 2HP from my Sea Pearl on it and it works great, although she draws 5 more inches and I hate the noise of that Honda with a passion. Has anyone encountered this? Take Care, Steve Quote Link to comment Share on other sites More sharing options...
Chick Ludwig Posted July 21, 2014 Report Share Posted July 21, 2014 Unless the keel is tapered down at the aft end, it will create turbulence which causes cavitation as soon as you start to turn.. Quote Link to comment Share on other sites More sharing options...
Alex Posted July 21, 2014 Report Share Posted July 21, 2014 No problem at all with my Suzuki 2.5. Quote Link to comment Share on other sites More sharing options...
Charlie Jones Posted July 22, 2014 Report Share Posted July 22, 2014 Please, please- It's ventilating, NOT cavitating. The plate on the motor is correctly an Anti VENTILATION plate. Stops the prop from sucking air down the outboard leg "Cavitation" occurs when props move fast enough to vaporize air from the water, and usually explosively, leaving little pits in the prop. http://en.wikipedia.org/wiki/Cavitation VERY high performance race boats have the problem Answer? Lower the engine more into the water. Quote Link to comment Share on other sites More sharing options...
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