BMW D-50

[Tommee]

15 mins after arriving at anchorage & turning off the engine, which had been running beautifully, I noticed the bilge pump going off repeatedly. On investigation salt water was coming out of 1 of the engine air intakes!! Further investigation showed a small amount of salt water in the oil & water in the cylinders. This has been expertly purged....injectors removed, engine turned over by hand until all water expelled, oil change etc.... & the engine has now started & run briefly (30-40mins) each day for a week. I am away from my marina & the engineer involved said I should turn the seacock off 7-8 secs before shut down & same after start up. There appears to be no water as yet in the oil or coming out of the air intake & hopefully I dodged a bullet & we guess this water ingress happened after stopping the engine & it had not run with water in it. Initially the oil level was slightly higher & did have water in it but showed no signs of milky appearance.
The engineer claimed my siphon system was a strange one & shouldn't work, however the boat is 38 years old, I have owned her for 30, sailed round the World etc & this has never happened before. He claimed I had 38 years of good luck. I don't buy that!!! Why would this engine suddenly do this?
Obviously when I get her home I can start taking things to pieces & checking.
Any guidance gratefully received.

[Bellinghamster]

Assuming the engine is mounted below the waterline - A clogged vent in the vented loop for the cooling water before it ports into into the exhaust injection point, combined with a worn seawater pump impeller. This will siphon water in from the intake, past the impeller up over the loop and fill your exhaust system until it backs up into the exhaust manifold, in through an open exhaust valve and down past the rings in to the oil pan (or in your case, the engine was stopped right where an exhaust and intake valve were both open - consider yourself quite lucky that it was apparent!)

I had it happen twice on a passage up the west coast of Mexico. After the second time, I removed the vented loop vent duckbill valve, screwed a hose nipple in the top of the loop and ran it into a cockpit drain.

The later fix (when I repowered) was to run dry exhaust pipe up to above the waterline before turning down into an injection elbow.

[VChild]

I had a BMW D50 in my Lord Nelson 41 before replacing it with a Beta 60. It was a great engine and I never experienced anything like what you describe. Maybe seawater backing up through the water muffler? I would talk to Rich Langtry at V12 Engineering in Canada. He is an expert on the old BMW marine engines and also sources the hard to find parts. His email is: langtry@bmwmarine.com

[Uncle Bob]

Originally Posted by Tommee

15 mins after arriving at anchorage & turning off the engine, which had been running beautifully, I noticed the bilge pump going off repeatedly. On investigation salt water was coming out of 1 of the engine air intakes!! Further investigation showed a small amount of salt water in the oil & water in the cylinders. This has been expertly purged....injectors removed, engine turned over by hand until all water expelled, oil change etc.... & the engine has now started & run briefly (30-40mins) each day for a week. I am away from my marina & the engineer involved said I should turn the seacock off 7-8 secs before shut down & same after start up. There appears to be no water as yet in the oil or coming out of the air intake & hopefully I dodged a bullet & we guess this water ingress happened after stopping the engine & it had not run with water in it. Initially the oil level was slightly higher & did have water in it but showed no signs of milky appearance.
The engineer claimed my siphon system was a strange one & shouldn't work, however the boat is 38 years old, I have owned her for 30, sailed round the World etc & this has never happened before. He claimed I had 38 years of good luck. I don't buy that!!! Why would this engine suddenly do this?
Obviously when I get her home I can start taking things to pieces & checking.
Any guidance gratefully received.

Perhaps a pic or diagram of the siphon system would help.

[manitu]

My D50 had a T-pipe just after the SW pump, with one hose going to the block, the other through the vented loop and to the exhaust manifold. Worked great until the SW pump decided to fill the crankcase with water through the seals.


.manitu

[FPNC]

This is a classic example of a failed exhaust system design. Despite the fact that it is 38 years old it needs to be examined and re-engineered if required. You need adequate drop to a lift muffler with adequate volume and an adequate loop over the waterline and out the exhaust port. ***The raw water supply needs a reliable vented loop that is well above waterline at all points of heel.*** Many vessel have a poorly designed system that 'just gets by' for many years with no issues. Then ultimately, particular conditions cause a failure.

[Tommee]

Very many thanks for all the advice & comments team. Much appreciated.