Is it steam ?

[HAS]

On a 1975 85hp Mercury 850, I run it on the hose for a short time and shut down to check compression.
When I removed the spark plugs what looked steam came out of the no. 1 spark plug hole, the compression
is 140 on this cylinder and 150 on no.s 2,3,and 4. If it is steam, what could be the cause?
THANK YOU.............HAS

 

[dish]

Re: Is it steam ?

Mate did the plug look steam cleaned??? Might be head gasket.

 

[HAS]

Re: Is it steam ?

No the plug was not clean, I`ll run it longer and see if it gets steam cleaned and post what happens.
THANKS....HAS

 

[Chris1956]

Re: Is it steam ?

There is no head gasket on that motor. If it does get steam cleaned, look at all the plugs and compare them to see which ones are steam cleaned. We can then guess what is wrong....