'78 90hp merc

[dragonfukker]

I am the recent owner of an 1973 ski boat. The boat came with an 78 90hp merc. The first time that I put it in the water I could not get over 7mph without a loud clunking noise coming from the lower end. The more I tried to put speed on the worst it got until I went back to the dock at idle speed. Anybody got an idea of what it may be. I am a pretty good mechanic but no outboard experience.

 

[Surfersteve]

Re: '78 90hp merc

I can surely tell you that you through your lower crank shaft bearing and that it made its was into cylinder number 4 or 6 if its a 6 cyl. Do not run it like this. It needs to be torn down and rebuilt. My 76 merc 850 had the same prob. Except my bearing busted two holes. one in the water jacket inside by rod number 4 and one in the crank cover.

 

[timmathis]

Re: '78 90hp merc

You must drop lower leg for inspection.<br />Get a manul first. Tim

 

[Chonguey]

Re: '78 90hp merc

^