Engine troubles

At the end of January we were planning on taking a trip down the coast. The boat was loaded up and ready to go but when I checked the oil in the engine it was milky looking. Water had gotten in there from somewhere. I changed the oil but the engine would not fire up. Had several people look at it but no one had any ideas nor did anyone have a compression gauge.

I finally bought a compression gauge and tested it. It was on the low end of what it should be but for a 25 year old engine that is not so bad. It should have been 284-355 with the starter but one cylinder was 280ish and the other 290.

Finally we got a nice day and I put a space heater in the engine compartment for about 3 hours. It surprised me by firing up almost immediately! I let it run for a few seconds and then stopped it as I had closed off the raw water intake. I opened that up and started it again let it run for about 20 minutes stopped it and checked the oil. It still looked new! I ran it a couple more times over the next few days and still no water in the oil.

I put some marvel mystery oil in the crankcase and put it in gear so the engine could get up to temp under load. Once I realized the thermostat was disconnected and fixed that the gauge went to where it should be. :)

So far the water problem looks like water backed up in the exhaust elbow from cranking it too much. I will change the oil again after I get the injectors cleaned and tuned. Right now it looks like the engine is working but hard to start in cold weather.

Things I have learned:
The specs say the Volvo Penta MD7B is 17 hp not 13 like the md7a. I don't know what else changed but all the manuals I found mostly referenced the md7a. Even the manual that came with the boat was for the md7a.

Even though I am in Florida a bit of extra heat on a diesel engine really helps a lot getting it started.

Getting a mechanic to look at a sailboat engine is hard. I only found one that would call me back and they wanted over $200 to compression test the engine. I bought a compression gauge for around $150 that I will likely never need again.