Fuel leaking into crankcase??

[jrmiller]

Hello,
I own #1211, a C34. It has a M35 diesel engine with approx 375 hours on it. The year of the boat is 1992. I have been noticing an increase in the oil level in the crankcase after operating the engine for upto 4 hours at 2000 RPM. I do have an Autoprop and it pulls a lot better than the old 2 bladed prop, thus, 2000 RPM is crusing speed not. I cruise at 7 kts.

After 4 hours of 2000 RPM operation, I pulled the stick and it showed 1/8" more "oil" in it than before. I went for another 3 cruise and it was up another 1/8". The oil is black in color, not milky so I am guessing that diesel is getting into the crankcase.

My first thoughts went to the fuel pump and perhaps a cracked diaphram, but this fuel pump is not mounted on the engine, it's electric.

I don't know diesel engines very well, but I do know gas engines and my next things to consider would be intake manifold, head gasket or perhaps a cracked piston ring. It has had regular oil changes (about 20 - 30 hours between oil changes), but it has overheated once when the impellor came apart. I shut the engine down quickly, but who knows what damage that may have caused. Besides, I beleive this oil problem began prior to that overheat. It was just less pronounced.

Has anyone had this problem?

Thanks,
John Miller
Delaware, OH

[Ron Hill]

John : I haven't heard of this in a diesel, but I'll guess that you've got a poor seals/tolerances in your injector pump -- especially if you've noted a power loss recently.  That's the fastest way for fuel to get into the crank case -- if the compression on each cylinder is within tolerance. 
I wrote an article (Mainsheet) on removing the injector pump from an M25XP and it shouldn't be that much different in an M35 engine. 
Think I'd call Joe Joyce at Westerbeake and see what he thinks.  He the top service manager.   

[jrmiller]

Ron,
Thanks for your reply. Actually, there is no loss in power, I can throttle up to the same engine speed as before and the boat goes faster than before (almost to 8 kts) which is a little past hull speed. Problem is the engine starts heating up, it normally runs around 170 degrees, if I put her on the floor, the temp climbs to 190. This is entirely because of the prop, the old 2 blader just didn't dig in very hard, the engine could turn that prop with little effort, this new Autoprop digs in like crazy, produces more speed, but heats the engine more. I will see a black puff every once in a while when pushing past 2000 RPMs with this prop. Never saw it with the old prop.

Are there passages on the injector pump that lead to the oil system?

I will call Joe, thanks for the tip.

-john