Is it possible for us to answer the question: How can infrequent, yet significant oil discharge be explained?
I think now, yes. Part of this is a recap of posts above.
First oil discharge cause:
The engine had the crankcase breather improperly installed when I got the boat. It was just led to open air near the intake instead of a nipple on a suction part of the intake manifold. This caused oil discharge over the years to soak my starter windings. MaineSail suggested an automotive air/oil separator which he has installed on many boats without problems. However, mine has both design and installation issues that make it particularly sensitive to crankcase pressure. Pitching the day before sent oil into the separator soaking the element and slightly raising the pressure. The breather is supposed to be under negative pressure on the engine anyway. I thought at the time I might not have properly seated the dipstick when changing the oil the day before but now think it may have simply popped out.
The causes of this incident were eliminated by removing the element from the separator, turning it into a simple liquid trap and finding the proper suction termination for the breather line.
High oil event this summer:
(Previously reported by not discussed in these recent threads.)
This along with excessive condensation and foam flecks in the liquid trap was, in hindsight, clearly the early warning of the head gasket failure. Very small amounts of salt water were getting into the oil.
Mount Hope Bay oil loss:
Sudden complete failure of the portion of the head gasket between the cooling and low pressure oil return passages.
Connecticut River Entrance oil loss:
Very slight over filling with oil by the mechanic in Portsmouth. No real fault of his, I was being conservative about the oil level, knowing about the oil issue. I believed him when he thought I could go a bit higher. It turns out I have been operating for years right at the limit for operating the engine in rough water. There was no way, without some complex measurements, that either of us could have known how close to the line I was. He did a great job overall. Oil contacted the crank in heavy pitching and was whipped into foam.
Partial oil loss at the dock that evening:
I still hadn't figured out the previous oil loss. I was also tired so I put in the same amount of oil without stopping to think that I probably hadn't gotten as much out of the engine as was done with the better equipment in Portsmouth. Oil also wasn't as hot when I pumped it out. Oil level was probably higher than before. Dipstick is very hard to read on this boat.
The engine "burped" out the lost oil in the last event. I haven't added any oil since. It seemed like a lot when cleaning it out of the drip pan and bilge but it wasn't very much. Dipstick hold down should now contain any transient overpressure.
The engine was also showing quite a bit of crankcase pressure the next morning, possibly due to oil or foam remaining in places. By mid morning, this had entirely disappeared. A similar hold over effect from the major oil loss at the river mouth may also have contributed to the dockside event.
I now have 56.5 hours of operation, including some pitching, with the dipstick level about 1/8" below where I have usually kept it.
It is now fully explained to my satisfaction.
In flat seas no problem in lumpy seas problems...........
