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.

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 ?

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 .

yep that's what I should have done HG. I just didn't think it through and assumed the battery was flat

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.

Trek 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.

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