Water Flooding Engine in Following Seas

[RDW]

I am reading a book on marine diesel engines by Nigel Calder. He discusses the risk of following seas pushing water up your exhaust and into the exhaust manafold, thru the exhaust valves and into the cylinders.
Has anyone experience this problem?
Has anyone used a oneway flap valve in the line or at the outside opening?
rdw

[Christian Van H]

See here: http://www.cruisersforum.com/forums/...ves-23538.html

[Fiveslide]

I don't have an inboard diesel or any experience with this problem on sailboats.

However, every ski boat that has an underwater thru-transom exhaust system has a setup similar to this...



Its purpose is to keep water from going in the exhaust.

I'm sure you could get something to fit your needs.

[never monday]

this issue depends on how the exhaust outlet presents to the water also.

If it's a flat transom with the outlet just above the water line it is possible. If you have a side exhaust or; sugar scoop transom, or canoe stern. Then the odds decrease exponentially.

[James S]

This is a very common problem...the flap helps...the valve stops it all together...but remember to open it before starting your engine.
There are many other solutions.
This has been discussed at length and the link from Christian Van H
Has some pretty comprehensive details.

[boatman61]

Usually there's a big loop going well above the water line in the exhaust hose, then the trap which is oneway..... stops most things..but then I'm speaking sailboats... this is a problem with st8 line exhausts I think... but if it helps you sleep easier fit a flap over your outlet....
Phil

[Joli]

It is truly amazing how quickly you can blow up a muffler with the valve closed!

Originally Posted by James S

This is a very common problem...the flap helps...the valve stops it all together...but remember to open it before starting your engine.
There are many other solutions.
This has been discussed at length and the link from Christian Van H
Has some pretty comprehensive details.

[hellosailor]

A flap "in" the line could easily jam and become an obstruction. A flap on the transom--is good cheap insurance and commonly done.

An actual valve in the exhaust line is more typically what someone would install expecting to go offshore and encounter storm conditions where you might literally need to button up the entire boat--tight.

[mesquaukee]

If you do install a valve it would be easy to install a switch in the ignition or starter circuit which would only allow the engine to be started or run when the valve is fully open.

Water coming back through the exhaust can happen even with a riser or loop (as Boatman61 suggests) that is well above sea level should you be in violent seas for extended periods of time as I once found out. If you suspect that there is water in the cylinders it is easy to vent the water out by depressing all the exhaust valves by placing shims between the rocker arm and exhaust valve stems (screwdrivers work) and then very slowly turning the engine over. Before doing this drain all water out of the exhaust manifold, etc.

[FloridaWriter]

Originally Posted by mesquaukee

If you do install a valve it would be easy to install a switch in the ignition or starter circuit which would only allow the engine to be started or run when the valve is fully open.

Water coming back through the exhaust can happen even with a riser or loop (as Boatman61 suggests) that is well above sea level should you be in violent seas for extended periods of time as I once found out. If you suspect that there is water in the cylinders it is easy to vent the water out by depressing all the exhaust valves by placing shims between the rocker arm and exhaust valve stems (screwdrivers work) and then very slowly turning the engine over. Before doing this drain all water out of the exhaust manifold, etc.

Or, simply open the decompression valves on the engine.

[eyschulman]

Cheap but shore method to prevent start up with valve shut-put a zip tie loop on starter key and loop this over the closed valve. when you open valve you retrieve key.

[maxingout]

When I had my Westsail 32, I have gotten water in the cylinder two different ways.

When the boat heeled way over in big seas, I have had seas go up the exhaust loop and fill up the muffler and cylinders.

I have also had failure of the antisiphon valve at anchor, and had water siphon on the intake side and fill up the muffler, exhaust elbow and get into the cylinders with open exhaust valves.

You have to get to know your yacht and take measures appropriate for your vessel.