1992 Mercury Outboard engine troubles

I have a 1992 60hp mercury outboard, there is a bit of a rattle that seems to be coming from the top piston i did a compression check and #1 is 90 and the other two are holding around 115.

The boat seems to run good no problem at high speed or just trolling or even pulling a tube I cannot say that the motor has not lost power as it belonged to a friend and recently just bought the boat off of him (but it does seem to run good) any idea of what this might be?? i did do a sea foam bomb or what ever you call it to try and get the carbon build up out, still running good but still have the clicking or slapping sound.

any advise would be great of what else i can check.

Thanks Trevor

Sea foam will not remove carbon. Sea foam is naptha, light oil, and alcohol, none of which will reduce or remove carbon in a combustion chamber. The slightly low compression on the one cylinder would indicate to me either carbon deposits, or a broken ring. I would suggest you first use a decarbonizer with a high percentage of PEA (such as Chevron techron, or Regane gumout), to try and free up a sticky ring. If the compression stays low, you're going to have to pull it apart for an inspection.

These motors are bad about sleeves slipping/turning especially if lugged and it not a carbon issue/problem. More likely sleeve has turned and ring has broken from hanging in the port. I fix about 3 of these a year and I drill and pin sleeves in place.

Question: With the sleeve moving like that, does that not mean pistons will seize from hot spot caused by poor cooling (sleeve not tight against the aluminum)?

I just had seizure # 2 from a block that already had a seizure (top hole each time) when I got it. I'm certain that is the case with this block.


Jeff

does that not mean pistons will seize from hot spot caused by poor cooling

Click to expand...

This is the looper motor,....No if sleeve turns the ring tip usually hangs in port and breaks or if slips it will back up and ring will fall behind sleeve and damage cylinder or lock it up.It does not cause a hot spot..

Gotcha.

Jeff