[jklancer]

Hello, I have a Mariner 150 late 80's, started blowing white smoke out of the exhaust ports above water below the power head. Starts and runs fine..go figure, after a couple of minutes the smoke starts (steam?). My wife was fishing, came in smoking. The temp was past the half way point on the gage but never went past the 3/4 point on the gage. (no temp degrees on the gage) I'm thinking head gasket on the V6. How do i trouble shoot. I don't think I can test the cylinder pressure like on a car enging. I'm mechanicly savy, but outboards seem to run on another set of rules.
If you could point me in the right direction, I'm not even sure it's a head gasket, except for the white smoke, I would appreciate it. I'm guessing my wife pushed in the key while starting it warm and maybe flooded it, then pushed up fast idle to start it. Don't know if that would contribute.
Thanks,
jimk

[j_martin]

Originally Posted by jklancer

Hello, I have a Mariner 150 late 80's, started blowing white smoke out of the exhaust ports above water below the power head. Starts and runs fine..go figure, after a couple of minutes the smoke starts (steam?). My wife was fishing, came in smoking. The temp was past the half way point on the gage but never went past the 3/4 point on the gage. (no temp degrees on the gage) I'm thinking head gasket on the V6. How do i trouble shoot. I don't think I can test the cylinder pressure like on a car enging. I'm mechanicly savy, but outboards seem to run on another set of rules.
If you could point me in the right direction, I'm not even sure it's a head gasket, except for the white smoke, I would appreciate it. I'm guessing my wife pushed in the key while starting it warm and maybe flooded it, then pushed up fast idle to start it. Don't know if that would contribute.
Thanks,
jimk

It's a motor. It's not "if" it'll break, it's "when"

If you pull the plugs and look at both the plugs, and at the piston tops, the ultra clean one is the bad one.

Water can get in through a bad head gasket, or sometimes through a leak in the exhaust chest, entering through the exhaust port. There have been cases of pinholes in the cylinder walls leaking water into the cylinder.

Compression test works just like on a car. Jam the throttle open, and crank. Be sure all the plugs are out and the leads grounded, and also crank it bypassing the key switch so it doesn't make spark. It should have about 120 lbs or so on each cylinder. If it's a bad head gasket, this will show it. If it's in the exhaust chest, probably not. Good info at any rate.

hope it helps
John

[jklancer]

Thank you john, just what I needed to know. If I get lucky and it's a head gasket, should I replace both head gaskets, or just the bad one and re-tourque the good one, or leave the good one alone? Can you recomend the best manual for my endevor, don't want to pull the head with out the un-touque sequence. I assume the head will have to be surfaced?
Happy Rowing....
jklancer