Water in Engine

[cipiti6]

We have a 4.3L V-6 Mercruiser engine with water in spark plug hole. There is no water in oil. Ran motor for 2 hours , when I shut down it backfired. When I went to restart it , it was locked up. I pulled plugs and alot of water came out of plug hole. Motor will turn over, not froze up. Where do I start to trouble shoot the problem? What are some of the causes?

[silverbullet02]

First guess would be a head gasket. What I would do until you find out is turn the motor over with no plugs in it and get the water out then spray some oil in the cylinder so it doesn't rust and cause additional problems in the mean time.

Brian

[cipiti6]

Thanks. I already put oil in cyclinders to stop any rust. I will check head gasket.

[Kings Marine nz]

How many hours on that engine ????
Could be exhaust manifold/riser rusted through..........
pretty common scenario from your diagnosis, do a leak down test to eliminate head gsk etc

[cipiti6]

How do you perform a leak down test? I'm not sure what it is.

[Greg Moss]

Some of those motors they put Stainless risers on. If you don't have them you need to change yours out. The cast iron ones rust through and which ever cylinder has the exhaust valve open will fill with water. If the boat as been sitting all winter you opened up the crack when you heated the motor up. I change Alot of manifolds and risers and I mean A LOT because of the water around here, Galveston Bay. If you run in salt water you need the SS risers and flush your motor with Salt-Away every time you come in,it really helps.