I a 350 chevy inboard. water is getting into my oil, and cylinder 6.?

Question

i drained the oil, and cleaned it the best i could. ran the boat for 4hrs. didn't overheat or run bad.

Answer 1

Previous answers have identified the source as a head gasket which is the most likely source.  A small defect in the head gasket (low level of water intrusion) will not be detectable in a 4 hour run.  While the engine is running the small amount of water will just go out the exhaust as a combustion byproduct.

It is the time when the engine is stopped that water will continue to leak into the cylinder and past the rings to end up in the oil.  After being stopped for a period, you may notice a miss on #6 when you first start and excessive exhaust smoke for the first 20-30 seconds.  The exhaust smoke is much harder to detect on a boat than on a car because you have the exhaust cooling water pumped into the exhaust.

After a few running and stopping cycles, you will again detect water in the oil.  It won't get better until the head gasket is replaced.

Answer 2

sounds like a blown head gasket

Answer 3

Other than the head gasket you might want to check the exhaust manifold.  A crack in the manifold will allow cooling water into the cylinder walls.

Answer 4

A blown head gasket could explain water getting into the oil or any of the cylinders.  To help out the engine you might want to change the oil several (3) times in order to get all the water out of the oil reservoir.  Of course you will want to stop the source of the water intrusion but you do not want to leave water in the oil reservoir that will cause rust inside the engine.

Answer 5

Could be blown head gasket or water leak in manifold as Breeze mentioned. best thing to do first is pull the plugs and do a compression test on all cylinders. You'll know right away what your problem is.