125 Merc Knock

[Gerrys57]

I have a 2001 125 Mercury outboard, several months ago I had a small problem with my oil injection, then one cyclinder dropped to 90 psi. I fixed the oil injection and compression went back up to 110 on all cyclinders. Now I can hear a knocking noise when I put the boat in the water, sounds like wrist pin. Is there a way I can check it without tearing down the motor. And where can I find free instructions on how to dissassemble. I'm an experienced auto mechanic but never touched an outboard.

 

[dbrew]

Re: 125 Merc Knock

the only real way is to get in their and check it out they arent that difficult to tear apart what is the compression on all the other cylinders? with that big of a difference and that noise i think you need to get in and check it out because if not you might just hear one final knock and then you have to buy a whole new powerhead.

 

[Gerrys57]

Re: 125 Merc Knock

Compression is 120 now on all cyclinders

 

[dbrew]

Re: 125 Merc Knock

120 psi in all but the one in question? usually i go with 10psi difference between the strongest and weakest so if the highest is 120 and the lowest is 110 you need to rebuild it especially if it was down to 90 and is making a noise now. sorry but better now than on the lake.