Water in the oil 1985 Searay 454/340

[peterd103]

I am looking to by this boat. One engine runs and one does not. The non-runner has water in the oil and the owner said it was making a strange noise when it quit. He says it was running under 1000 RPM when it stopped and it did restart briefly. No chance to pull the plugs or do a compression test. I know it's a crap shoot. I know it is either cracked block, cracked head or blown head gasket. Any known issues with these engines? Any thoughts would be appreciated. Thanks. BTW I am a mechanic but mostly work on diesel trucks.

 

[kenny nunez]

Are the engines fresh water cooled? If so check the coolant level. If the coolant is full then it might just be an exhaust manifold riser.
I they are raw water cooled it could be plenty of things. Since you are a mechanic pulling the plugs as you said would be the first place to check.

 

[peterd103]

I should have mentioned they are raw water cooled.

 

[Scott Danforth]

Assume both motors are toast as the non runner with water in the oil has sat for more than a day or two with the water and will need a complete overhaul. The running motor is probably suffering a bit as well. A compression test on the running motor will verify

You do not state if this is fresh water or salt water boat. Going to assume salt water.

It's almost never a head gasket or a coil. In this case, either failed exhaust (common on all salt water boats), or a failed winterization

The Mark VI BBC was the same from 1965-1990. The only known issue is lack of maintenance will kill them and any motor.

The mid 80s motors are probably low compression motors.

 

[peterd103]

Assume both motors are toast as the non runner with water in the oil has sat for more than a day or two with the water and will need a complete overhaul. The running motor is probably suffering a bit as well. A compression test on the running motor will verify

You do not state if this is fresh water or salt water boat. Going to assume salt water.

It's almost never a head gasket or a coil. In this case, either failed exhaust (common on all salt water boats), or a failed winterization

The Mark VI BBC was the same from 1965-1990. The only known issue is lack of maintenance will kill them and any motor.

The mid 80s motors are probably low compression motors.

Born and raised on Lake Michigan. Thanks for your input.