94 4cyl Mariner

[Mike722]

I have a 1994 4cyl 40hp Mariner outboard ser# 0G048873 that we put about 55 hours on last year and have run about 1.5 hours this year. The engine starts and runs fine.

We purchased a new E-Tec because we wanted something with less fumes and noise. The dealer checking the motor over for a trade-in price found that the compression was good on all cyls, but the number 3 has about 30% leakage on the leak down test. My question is a rough quess on how long that engine would run before major engine failure? I know each engine is differant and that it could run a short or long time this way, but I was curious about what others experiences have been.

Thanks
Mike

 

[Laddies]

Re: 94 4cyl Mariner

Leakdown means nothing on a 2 cycle engine, if the compression is even (10%) Mercury for years didn't even list compression specs. for their engines

 

[WillyBWright]

Re: 94 4cyl Mariner

Actually leakdown can be a somewhat valid criteria. It might indicate some minor flash scoring which is not at all uncommon, or it can indicate carboned rings. A decarboning treatment could easily cure the latter.

Leakdown is rarely done on 2-strokes. I don't put much stock in it. 2-stroke rings are designed to seal best under load. Leakdown is rather normal and I'm aware of no specifications of what is or is not acceptable. I would fully expect significantly higher percentages than 4-strokes to be perfectly acceptable because of the style of rings used.

 

[Mike722]

Re: 94 4cyl Mariner

Thanks for the info. I just got back from picking up the boat and old motor. I talked to the mechanic and it was the number 1 cylinder and he said he could see scoring on the walls. This is the same cylinder that my other dealer said had low cold compression last year when the stator was bad.

The good news was we were replacing the motor anyway and it didn't leave us stranded at the far end of lake.

Thanks again.
Mike