Went to start my trusty little Bukh and it wouldn't turn over, I thought that's strange I have a brand new starter motor and a new engine 100 amp hour AGM engine battery, but having done all this before with a cactus starter motor and marginal batteries I just went into auto mode and flicked the switch to engage my 3 house batteries all new 100 amp hour agms.
Well those 4 batteries and the brand new starter motor were enough to turn the engine over and spew about 2 litres of water out the exhaust.
The engine ran for about 3 mins and then spluttered and died and then spat oily water out of the air cleaner.
Now I have water in the oil and am hoping that all I need is a new head gasket.
Bukh were happy to tell me they had new heads in stock for 2 grand. 
The head comes of tomorrow fingers crossed.
Hi Andy-You may have possibly had back flow of water from the exhaust into the engine.
The S/S 34's have their engine mounted very low in the yacht(below waterline) and all water plumbing is critical in these.
You probably know all this anyway, but vented loops as high as you can get them are the go!.
Thanks for you advice Cool Runnings
There is a vented loop fitted but it is not that high (it runs back under the companion way stairs and is only 200-300 mm above the elbow) it was spurting water out of the cap a few months ago so a bought a new loop fitting and screwed the new cap on to the old fitting.
It stopped the leak but maybe I screwed up there and allowed the water to siphon through ?
I feel for you Andy, as it's a rotten predicament.
We had sailed to LHI some years back and on Port tack all the way from the Gold Coast, the slop had filled the exhaust up with seawater and back into the motor.
As we arrived at the lagoon, it became apparent the engine wouldn't fire up and were up to our arms in diesel, cracking injectors open and so on.
We did get it running on the last couple of amps left in the batteries and so all was well again.
A beer never tasted sweeter when we pulled up the mooring at the North Passage!
I'm wondering if you doing the same may achieve something easier then taking off the head.
Perhaps also checking the dipstick for signs of 'milky' oil?
Regards,CR.
The anti syphon in mine blocked up with similar results . I got rid of the vent cap and made a cap with a small hole with a hose tail . Ran the hose up into the cockpit over the drain , when the engine runs it weeps like an out board that way I know its all good .
Water in the combustion chamber
If you ever think that might have happened Andy I turn the motor over with the decompression lever down either with the hand crank or the starter motor
Next time 
yep that's what I should have done HG. I just didn't think it through and assumed the battery was flat 
Select to expand quoteoldboyracer said..
The anti syphon in mine blocked up with similar results . I got rid of the vent cap and made a cap with a small hole with a hose tail . Ran the hose up into the cockpit over the drain , when the engine runs it weeps like an out board that way I know its all good .
Thats's a good idea
I might fit something like you made. Are you suggesting fit your cap and tail gadget at the top of a riser in the exhaust somewhere after the cooling water enters the exhaust pipe system?
I designed my own exhaust which has worked OK so far. Out of the engine (Volvo 2003 28hp) is a riser 0.5m higher than the sea level outside, after that riser the used cooling water is injected, then theres a big boof box, then 3m of exhaust hose down to the stern, then a 0.5m up and 0.5m back down plastic muffler. The actual exhaust outlet is 0.5m above sea level unless the stern gets hit by a wave.
I imagined seawater could never get past all that but I guess on long trip maybe it could.
You just solved a puzzle of mine on MB. Mine has what was described as a tell tale in the stbd cockpit drain where the engine cooling water comes out, as well as via the exhaust, when all is well. I assumed it was a convenience thing. It is as you describe so now I know why it is there.
Select to expand quoteTrek said..
I might fit something like you made. Are you suggesting fit your cap and tail gadget at the top of a riser in the exhaust somewhere after the cooling water enters the exhaust pipe system?
I designed my own exhaust which has worked OK so far. Out of the engine (Volvo 2003 28hp) is a riser 0.5m higher than the sea level outside, after that riser the used cooling water is injected, then theres a big boof box, then 3m of exhaust hose down to the stern, then a 0.5m up and 0.5m back down plastic muffler. The actual exhaust outlet is 0.5m above sea level unless the stern gets hit by a wave.
I imagined seawater could never get past all that but I guess on long trip maybe it could.
My understanding is that, for a raw water cooled engine, if the exhaust valves are lower than the sea level then sea water can siphon back through the loop into the cylinders. So the loop needs an air brake or one way valve to stop the siphon effect. In my case, I put a new cap on the valve because it was leaking, in doing so I allowed sea water to siphon into my cylinder.
Without fail when starting my engine I decompress the cylinders and turn it over 4 times before hitting the starter button.
Benefits.
1. Proves the engine against hydraulic lock.
2. Puts a few squirts of diesel into the cylinders creating a fuel rich mixture much like using the choke on a petrol engine.
3. It just lets you know the engine is turning freely before hitting it with starter motor grunt.
Im just saying. ....all great info
All I can add is if u start a motor each day
U dont seem get these issues. ...imo
Select to expand quotecisco said..
Without fail when starting my engine I decompress the cylinders and turn it over 4 times before hitting the starter button.
Benefits.
1. Proves the engine against hydraulic lock.
2. Puts a few squirts of diesel into the cylinders creating a fuel rich mixture much like using the choke on a petrol engine.
3. It just lets you know the engine is turning freely before hitting it with starter motor grunt.
That's one advantage to having a decompression lever on your engine. My Volvo Penta D1-30s seem to be lacking in this department, unless it is well hidden.
