Logo
FULL SITE MENU

1983 Mercury 150 outboard low compression in two cylinders

C

curtis63

New member
Overheated my Mercury and blew a hole in the head. replaced the head. motor runs but is down to 45 pounds in one cylinder and 75 pounds in another. the rest are around 95-100.

I don't want to do a full rebuild. Are there any tricks to loosening up the piston rings without taking the Pistons out? And how long you think this motor will last as it is? it does run.

Will running this way do further damage or is it an anchor already?
 
Its hurt so start saving for rebuild or replacement. IMO its too old to repair as you can finds a 2.5 for a little extra
 
any magic chemicals or fluids that I can add to the gas or dump into the cylinder to free up the loose rings and thus regain compression ?
 
No, it sounds like you are way beyond the power of "ring free" - sounds like you have some "mechanical damage" that also occurred because of the overheat that you had not addressed.

I personally would not run a motor in this state, but it's certainly up to you. It may work (kinda sorta) for a day, a week or even a month. Or you may put another hole in it, this time the block when one of those low cylinders causes a rod to go through the side.

I likewise wouldn't put the money into this motor to rebuild it unless 1) you can do it all yourself AND 2) you have already sunk a lot of money in it in the last year or so.

I won't judge the maintenance level based on your overheat that caused the issue in the first place, but if it overheated because you hadn't got around to servicing the waterpump for a few years then you might want to shop for something else. There are a good number of big 2 strokes in the used market, and since 4 strokes are the flavour of the day you might pick one up that's at least 10 years newer than what you have for not a whole lot more than the cost of having this rebuilt in a shop.
 
Back
Top