Northen light generator 753 K on GB 42 C

[Gypsymagic]

I have a 1996 NL 753k with 4k hours on a boat I purchased 12 months ago. It ran fine, oil analysis at purchase showed normal wear. After about 300 hours it started to smoke, white.
I had valves adjusted, installed new injectors, cleaned exhaust elbow etc. Smoking got worse and fuel residue started showing out of the wet exhaust. Readjusted valves, had new injectors tested and still smoke and fuel. Engine ran fine for hours even with full load. I did a compression test and had one cylinder with no pressure, one with 350 and the third one at 460. I cut the fuel off on the cylinder with 0 pressure, and surprisingly the engine stopped smoking and no fuel trace, and ran just fine on the other two cylinders.
Any thoughts on the problem?
Thanks

 

[lwarden]

My guess would be a bad valve. Can you do a leak down test on it?

 

[twistedtree]

My guess would be a bad valve. Can you do a leak down test on it?

Yes, and hopefully just a stuck valve that can be freed up.

 

[lwarden]

I have this same generator, it's a very nice little unit and the engine is very robust. Since you already the valves adjusted I would suspect a stuck valve would have been noticed, but maybe not? Anyway, since you already had the injectors out and the valve cover off if you can get an adapter for a leak down test to go into the injector hole a leak down would be simple to do. If it's a bad leak, and from the compression test it sounds like it is you can likely hear the air going into the intake or exhaust side by removing the air cleaner or exhaust hose. Good luck.