Three weeks I bought a new (used) boat. I swore I would never buy another boat but here I am. Any way I purchased a used 1991 Sunbird with Johnson 90 motor. I have been around boats but not outboards so this was all new. When I purchased the guy said it would not idle in gear. Sure enough he was right. I started with the obvious check fuel. It was ok. I went to spark. They all checked out. I decided to do carb rebuild. I done this and put new plug wires on it. It started and ran better. Took it out to the lake and it ran fine for about three hours and then about did not make it back to dock. Brought it home and put it in the pond to test out. only way it would idle was to advance the spark so far that it should not be running. I got curious and pulled the plugs. Sure enough guess what I found. Water...... Did compression test three cylinders were low. Remove both heads and Head gaskets were gone. I have no idea how it ran at all on the lake. I had the work order where the previous owner had had it checked and they said compression was fine. This was a month ago. IDK???? Anyway after countless hours of reading and learning outboards I finally got it running good. I just wanted to post this up to help any others out there. I read numerous post with same symptoms. Although this will not fix all of those it is a reminder of another possibility to fix it.
If any one is attempting to work on there motor and do not have a service manual. BUY ONE. It is a must. I have Two one for in the house and one for the shop.
If any one is attempting to work on there motor and do not have a service manual. BUY ONE. It is a must. I have Two one for in the house and one for the shop.