1995 120 hp force low compression

[slammed2000]

i have a 95 hp force that has 10psi in to cylinder but runs fine. starts right up and makes no noise. any idea on where i should look first to fix problem.

thanks

 

[Frank Acampora]

Re: 1995 120 hp force low compression

These engines will start and even produce some useful power with one dead cylinder.

I hate to tell you but with 10 PSI on one cylinder, you either have stuck rings (usually due to overheating and piston galling), deeply scored cylinder walls, or a melted piston due to detonation.

Since you have already done a compression check, the next step is to remove the cylinder head and assess the damage. I doubt that a dose of Sea Foam to decarb will do anything so don't even bother with it--it will just be wasted money.

More than likely, with compression that low, you will need to overbore the cylinder, which requires disassembling the engine.

If you find a melted piston, be sure to check the carb to prevent it from happening again on the new piston.

 

[roscoe]

Re: 1995 120 hp force low compression

head gasket.

 

[Spinkick]

Re: 1995 120 hp force low compression

These engines will start and even produce some useful power with one dead cylinder.

I hate to tell you but with 10 PSI on one cylinder, you either have stuck rings (usually due to overheating and piston galling), deeply scored cylinder walls, or a melted piston due to detonation.

Since you have already done a compression check, the next step is to remove the cylinder head and assess the damage. I doubt that a dose of Sea Foam to decarb will do anything so don't even bother with it--it will just be wasted money.

More than likely, with compression that low, you will need to overbore the cylinder, which requires disassembling the engine.

If you find a melted piston, be sure to check the carb to prevent it from happening again on the new piston.

This is so true. I bought my 1998 Nitro with Force 120 a year ago from someone that knew less about outboards than me. I took it out 3 times and had so little power (25mph max), but the motor ran. Checked compression and found 0 on #1, about 20 on #4, and near normal on #2 and #3. #1 had a hole in it...big one too. #2 was badly scuffed Apparently it had been run for a while without oil in the gas. After $3600 top-to-bottom rebuild with new crankshaft, head, and oversized pistons, it runs much better. Hope yours isn't as bad off as mine was.