64 evinrude 90hp high speed vibration

[JG18]

hello,<br />I have a 64 90 hp. Evinrude on a 1961 glastron. I've be working on this boat for most of the summer and have got it running great. before this year the boat sat for 15 years. <br /><br />Okay here's my question, on wet dock I can run the motor at any speed (in gear) without any vibration, smooth as silk baby!! but, when I take to the water I get to about 3/4 trottle every thing is good. When I go over 3/4 trottle the motor starts to vibrate very badly. feels like trans slip<br /><br />Prop positioning??

 

[DJ]

Re: 64 evinrude 90hp high speed vibration

JG,<br /><br />Is your prop bent? Perhaps the prop hub is starting to slip.<br /><br />Also, check the run out on the prop shaft.<br /><br />Are you sure you don't have a cylinder dropping out. Coils can break down under high speed/load.<br /><br />Engine height can cause problems. Is your cavitation plate close or even with the bottom of the boat?