Water in cylinders--Have a theory--Whats your thoughts?

[Moose]

So here's what happened. Boat was overheating on the lake so i shut it down to investigate. Plenty of water going into the engine probably a stuck thermostat. Went to restart and the engine made about one spin then wouldn't turn over at all. Was thinking the worst (seized) Got the boat loaded and started pulling spark plugs. Found water in every cylinder the rear downhill one's had the most. Got the boat home and started pulling parts. Intake manifold good. Intake Gaskets good. Exaust manifolds had water in the exaust ports. Pulled the heads both of them look great. Head gaskets look almost brand new. Block looks great no cracks visible anywhere. Piston tops look brand new. Engine only has about 100 hours since rebuild. Engine was winterized properly plus no visible signs of a freeze. No water in the oil. Every cylinder has great compression. So here go's my theory Either the gasket in the exaust manifold that seals the two sections right at the elbow burned out or my exaust flappers that look like their due to be replaced let water get sucked into the engine when i shut it down. I have heard of this happening to trucks when the exaust pipe is under water and the engine is shut off. The hot engine sucks the water up and into the cylinders. The amount of water i found in the cylinders would indicate either a catostrophic faliure which didn't happen or maybe my hot overheated engine sucked up water through a burned out exaust elbow gasket or straight up the pipe.

Has anyone had this issue with a thru hull exaust boat before? Anyone have any ideas or thoughts? I would like to hear them.

[docdrs]

Interesting situation. First tho , if the engine was getting lots of water why did it overheat?

[Moose]

I belive the thermostat got stuck closed in the housing. It was pretty crusty. But i'm not 100% on that.

[DKJBama92Mariah]

Exactly how bad are the flappers? Pics would be great.

Also, how hot was the overheat? Where was the temp gauge.

A hot engine won't just suck water up the exhausts into the manifolds and cylinders, but the flappers do serve a purpose. There are two main way water can be forced up the exhaust and into the cylinders. First, if while stopped you catch a big wave to the transom with the engine off, the wave can travel up the exhaust pipes into the center of the riser and down into the manifolds to the exhaust valves. Second, if the engine is shut off while the boat is up on plane without idling down first, the trailing wave that forms behind the boat will crash into the transom. Without flappers or engine exhaust to stop it, this wave will also travel up the exhaust pipes and into the manifolds. Flappers in good condition protect the engine in both of these scenarios.
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Also if the manifold do get flooded, the engine doesn't immediately lock up because only a couple of exhaust valves are open at any one time. But once the water it in the manifold, it will sit in the runners until the exhaust valve opens. It would take one or two turns of the engine, just as you described, for all the valves to have opened and completely lock the engine up.

Does either of the two situations fit you? Flapper condition is critical here. We NEED to know how bad they are.

I would get some sort of oil into those cylinders pronto to keep the cylinder walls and rings from rusting. Also check the oil for water contamination. You will want to change it before running it again anyway.

I really don't think you burned though the riser gasket. It is made of some pretty resilient stuff. It seemed almost like lead when I scraped it off the last time I had my risers off. I'm pretty sure if you got it hot enough to burn through that gasket, it would cook the exhaust hoses on the manifolds. You'd know it if you did that, those hoses smoke and stink when they start to melt.

[DAFF]

I wonder if the engine dieseled a tad on shut down and made the engine turn in reverse sucking the water in the manifolds into the engine. I could see the cooling effect pulling water in too but there would beed to be a plug on the top of the carb for it to happen....

[jet]

?? man haven't heard of this one before?? I have heard (not sure if its true) that manifold gasket in the middle of the manifold keeps the water out so If It fails, water in the engine?? Keep us informed. New engine?? Man that hurts. Sorry man.

[Moose]

DKJ My flappers are intact but because of their age the flapper part sticks out at a 30 deg. angle so I belive on engine shut down they are staying open but they would still close on a wave situation. Dont know if the engine could suck the water that far but some of the exaust is under the water line so with flappers open it would fill them anyway. After stoping the engine when I went to restart it did make about 1 to 1 1/2 spins before it locked up. Later I found water in every cylinder the rear downhill ones had the most. Durining tear down I had some water spill out of the exaust manifold at the ports. That plus not finding any evidence of a failure leads me to the engine taking a drink sceniero. Haven't had a chance to pull apart the exaust risers yet. Right after this happened and i pulled the plugs and spun the engine over a couple times to squirt out the water then used a whole can of fogging oil in the intake, and spark plug holes while turning over a couple more times. The other day when I pulled the heads I didn't have any rust.

The oil looks good not milky and I can't see any signs of water but i will change and flush a couple times with fresh oil when I get it running. Exaust hoses didn't burn.

The engine taking on water through the exaust is the only thing I can come up with for what happened. Everything else looks great. I can find no signs of any other failure.

Thanks guys for your input I will keep ya updated on what I find and I will take some pics. of the flappers. Now I'm gonna go spend some money with skidim.

[docdrs]

Is this a salt water boat?

[Moose]

Nope fresh water.

[csuggs]

My first thought when I read the thread was your engine spun backwards. Not sure how this happens, but I've heard of it. And the flapper condition doesn't necessarily matter because even with the flappers closed, there's enough water in the exhaust manifolds and hoses to fill the cylinders.