Strange noise merc GM120 engine

[JOHN_T_65202]

I have a strange noise in my GM120. from 2200 rpm to 2500 rpm there is an engine noise that roughly sounds like a loose flywheel cover or some other thin steel. The strange thing is, it only appears within that rpm range and it sounds like it is internal. That is also a very small range. any ideas?

 

[JOHN_T_65202]

More Info

More Info

Located the noise as coming from the starter. It has just been replaced within the last couple of years it looks like. Could someone have left a shim out maybe?

 

[Don S]

Re: More Info

Re: More Info

Is it one of those gear reduction starters? Is there a grind mark on the housing where it hit the flywheel?

 

[metwrench]

Re: Strange noise merc GM120 engine

Could be a Lazy Starter Drive not being Pulled Back due to rust or Scaling. Is the Starter easy to Pull ? I would get it so its Making the Noise, Shut the Motor Down and Pull the starter...Then Look at the Drive gear and Ring gears and see if they are Showing Shiney Spots from hitting. Note the Distance the Drive gear is out from the starter Housing and Then try and Push it back and see if its Hung Up...

 

[Bt Doctur]

Re: Strange noise merc GM120 engine

Flywheel dust cover cracked?

 

[JOHN_T_65202]

Re: More Info

Re: More Info

I can see no marks of any kind and the only label on the starter says "Marine Starter 7F37"

 

[snake91876]

Re: Strange noise merc GM120 engine

just fixed this same problem on an 87 merc 3.0l i found that for some reason the aftermarket starter did not fit up exactly right though i couldnt tell. the hanger on the back of the starter that mounts the starter to the block had been removed like on all old boat engines. so i loosened starter bolts made me a hanger out of strapping the kind with the holes in it thats about 1" wide from lowes to pick up the starter rear slightly. just a hair. then tightened starter bolts back. fixed everything after weeks of trying my noise is gone at all rpm ranges.

 

[Bondo]

Re: Strange noise merc GM120 engine

Flywheel dust cover cracked?

Ayuh,......

That would be My Guess.........
Or,...
Bolts Missing from it.....

 

[JOHN_T_65202]

Reply

Reply

Thanks. I'll try that.

 

[JOHN_T_65202]

Re: Strange noise merc GM120 engine

Tried that fix. all I have done is to move the range up the scale. It now does it between 3000 - 3300 rpm. What do you think, should I just pull the starter and see if I can see anything obvious?