I think I would get a second opinion from another mechanic. I have really thought about this and struggle to see how fresh water can mix with your oil when there is no connection to fresh water. This is about as absurd as finding engine oil in your drinking water.
While I can’t think of any cause for fresh water, if the muffler failed it would still be saltwater. So, the mechanic is talking out of both sides. And, if someone stuck a water hose in the exhaust hole to sabotage the boat then wouldn’t the engine also have water in it as it uses the same exhaust? Is it possible the mechanic lacked taste buds and couldn’t tell the difference from salt water and fresh water? If so, was the generator cranked without starting (the easiest way to fill the generator with saltwater)?
With best regards,
Sailing Vessel - Cream Puff - SM2K - #275
Currenlty cruising – Turks and Caicos Islands
Update: A mechanic came and in draining the oil found a lot of fresh water,before the oil started draining. He pulled the plug on the vetus muffler and it seemed full, in fact he could hear water gurgling in the engine to muffler hose.
Apparently the muffler failed.
What's surprising about this is it an fine the last time just before we were hauled out. Now it has water in the engine. All the exhaust hoses look fine, no evidence of excessive heat.
The mechanics only real theory is that the muffler failed. The other was that someone purposefully stuck a hose into the exhaust from the outside and forced water into the engine.
They plan on filling the engine oil reservoir with diesel fuel overnight, and then turning the engine by hand to check for water lock. He noted the only way for the water to get into the oil was through the cylinders and rings. They're going to replace the muffler as well since it had to fail for this to happen. Apparently there's not much else to be done.