1977 sears eska ted williams 9.9

[hewie]

I have a 1977 sears esak that was givin to me and it runs great! But the problem is at a idle the motor has no vibrations but when it gets to bigher rpms it starts vibrating and just before it starts getting to plane the motor sounds like it has no more power and then all the sudden the engine reves up and bow comes down i took the lower end apart all good checked linkage thinking it was jumping out of gear still ok then i checked prop shaft looked straight to me im no marine tech but i am mechanically inclined so i then put a board close to prop and rotated it to check blades and none seemed bent could the prop be cavitating bad enough to cause the bad vibration and motor reving up? Please help i think that its a easy fix but i know nothing about boat motors but you get me under the hood of a vehicle i can fix it.
Thanks

 

[brim_buster]

what plug are you using and what oil/gas ratio? You have to remember its a lawn mower engine. And when you say it revs up does it die after that or just revs up? Almost sounds like its running out of gas at high rpms.

 

[hewie]

Champion r19 ty i think is the plug and mixed at 50:1 like it says on motor tag it never does die or sputter at all just vibrates real bad and looses foward momentum im at a loss

 

[hewie]

I might have figured it out i think it was the rubber between the prop and the metal that drives the prop the buffer bushing as its called have yet to get on the water though