hydro lock

[scottberry]

I have a 5.7 mercruiser that is having a hydro lock issue. Last week after a successful day of boating we were sitting in a cove swimming. A few big waves came at us and hit the boat from behind. I have through hull exhaust so there is a possibility some water could have passed through.

A little later when I went to start, the starter grunted and then was spinning but not engaging. I had to get towed back, but at least it was the end of the day.

I started breaking down the issue and removed the plugs. A little water dripped out of the center two cylinders on each side. I turned the motor over and a little more came out but not a significant amount.

After replacing the starter and plugs and putting new exhaust flappers in the the through hull pipes, it started right up and ran perfect in the driveway. It started and stopped several times with no issues at all. I took it the lake to water test which was about a 30 minute drive. By the time that I had launched the boat in the water, the starter was binding again. I pulled it out of th water and removed the plugs again. As I turned it over, a little water came out again. Mainly out of the two center cylinders on each side.

So if it appears the motor is running fine, how is the water getting into the cylinders and causing the motor to hydro lock and bind up the starter.

When I first checked the oil it was fine. Now after running it, there is a slight milky texture but not that bad. It is not all foamy in the valve covers and the dipstick does't look like a vanilla shake.

Any thoughts or suggestions??

Thanks

 

[diehard]

Re: hydro lock

i would start by taking a compression check just to make sure that is ok..then i would look at exhaust manifolds how old are they ? could be a coincidence that your boat was rocking at the time you got water in...

 

[scottberry]

Re: hydro lock

The exhaust and risers are about 2 years old. I did have a couple of overheating issues once this year and one last year due to the impeller failure.

I pulled the risers off to check the gaskets and they were a little worn. I did notice some water in the bottom of the exhaust manifold when I looked through the larger hole that the exhaust uses.

How does the water get in the exhaust manifold? Through a leaking riser gasket or through crackes in the manifolds?

If that is the case, why did it just start now? I have been out several times since the overheating and had no problems at all. I was out the whole day when the starter locked up. That is why I attributed it to the water in the exhaust.