Motor Question `965 Johnson 90 HP

[jwelters]

I just purchased a 90 HP Johnson 1965 model with the electric shift. After some repairs to the controls the motor starts and runs fine. However once the boat starts to move pretty good the motor revs up and slows itself down. The motor is on a 17' 1971 Sea Ray.


In the past I had an 85 HP Evinrude, and the motor had two gears and would automatically shift when you got going about the same speed as I have my problem.

What are your thoughts, it could very well just be that the motor is cavitation out of the water but I just don't know. The water pump is weak so once the new impeller comes in I'm going to throw that in along with one of those "wings" (for lack of knowledge of a better word) to see if that helps out.

 

[R.Johnson]

Re: Motor Question `965 Johnson 90 HP

Compression first, then check fuel flow. OMC never made a self shifting, or automatic gearcase. I don't know what that 85 was doing.

 

[denlou]

Re: Motor Question `965 Johnson 90 HP

If I'm understanding you correctly, the motor is reving up and the boat is slowing down.
It could be cavitation or it could be the forward clutch that year/model had.
I don't know alot abt. OBs but I had that same year and model and the clutch/gear is a spring and knurled drum where the spring tightens around the drum when you shift.
This arrangement had a habit of slipping, wearing the spring and or drum.
Water in the lower unit oil was a fast way to destroy these clutches.

For your sake I hope I'm wrong because their not cheap.