Hydro lock in cylinder 6

[Swampy1229]

hello to all I have a 1997 5.7 carborated mercruiser .the block and heads were recently rebuilt by a reputable machine shop and mechanic.the engine runs great but after sitting a while she locks up upon trying to re start. The #6 cylinder is the only cylinder compromised with water and there is water in the oil(milk shake). I have new manifolds and risers and have changed the flappers. The block was “supposedly” manga fluxed and I even swapped out the head on the starboard side. Is it possible for water to get into only one cylinder from the intake manifold(corossion or crack) it’s the original intake. Other than the machine shop missing a cracked block what else can it be?

 

[Scott Danforth]

look at your exhaust

most likely your gasket joint between the manifold and elbow have failed, or you have a crack in the manifold

 

[Swampy1229]

Every thing new!

 

[Rick Stephens]

First - magnafluxing isn't perfect. It only gets places you can see. There are more places that can't be seen on a block than can. So the machine shop only does its best to find any cracks but can never be 100% sure. The real way to see if you have a crack or a intake leak is to cap off the water lines going to the exhaust manifolds, remove the in-line from the thermostat housing, this is the line coming up the port side of your motor from the outdrive. Make up a fitting there with a gauge and a schrader valve and put 15 pounds pressure on the block and see if there's a leak internally.

 

[Swampy1229]

Thanks Rick....Do you know if it’s possible for water to get into a cylinder from a bed intake manifold it’s really the only other component that I haven’t changed I’m just trying to cover all the bases before I pull the engine on Wednesday

 

[Rick Stephens]

Thanks Rick....Do you know if it’s possible for water to get into a cylinder from a bed intake manifold it’s really the only other component that I haven’t changed I’m just trying to cover all the bases before I pull the engine on Wednesday

Not as likely as something in the exhaust or heads. But possible. Usually intake leaks dump direct into lifter gallery. Make sure you pressure test before pulling heads or intake. I made the mistake of disassembling before pressure testing and had to rely on magnafluxing to make sure I didn't have a cracked block. A simple pressure test resolves that question. Once you pull the motor down it is too late to test.

 

[QBhoy]

Most likely the exhaust and or riser or the head gasket perhaps. Only saying this as usually there would be water in more than one cylinder if it’s the exhaust and certainly of it was the intake manifold, I’d think.
presumably the block isn’t frost cracked in the usual place just below the intake manifold or on the outside of the block ?

 

[Swampy1229]

Nothing visibleOn the block. Engine was magna flux every component new including risers and manifolds flappers head gaskets same result Hydro lock just in cylinder six and milkshake oil

 

[Scott Danforth]

because you have water coming into the exhaust on cylinder #6 and working past the rings to the oil.

pressure test the system to make sure its not the block or heads

 

[tank1949]

hello to all I have a 1997 5.7 carborated mercruiser .the block and heads were recently rebuilt by a reputable machine shop and mechanic.the engine runs great but after sitting a while she locks up upon trying to re start. The #6 cylinder is the only cylinder compromised with water and there is water in the oil(milk shake). I have new manifolds and risers and have changed the flappers. The block was “supposedly” manga fluxed and I even swapped out the head on the starboard side. Is it possible for water to get into only one cylinder from the intake manifold(corossion or crack) it’s the original intake. Other than the machine shop missing a cracked block what else can it be?

If salt water boat, cancer may have eaten inside head away from water passage to combustion chamber. It happen to me. It is my understand that fresh water engines last a lot longer. You may have just blown head gasket. If fresh water engine, u should pull head asap and recycle with new oil. Hopefully this will save motor. Some of my boating friends over the years have had some success in draining contaminated motor oil and filling with diesel oil while identifying issues.