4LH DTE white smoke

[Forrest Bogue]

Bought a an old boat that was repowered in 2000 with Yanmar 4LH DTE’s. Wasn’t propped right (only spinning 3050 at full RPM light load) so propped to the recommended 3300 (under load). Boat has done me well for almost 2 years but recently port engine has started smoking white bad with a sheen in the water. Not sure if it’s fuel or oil. I seem to be burning coolant (reservoir pretty low and topped off recently) and smoke only gets worse with RPM increase but no loss of power. No water in oil pan on the dip stick that I can see. Compression test was good but need to do a leak down test. Injectors were removed, pop tested and cleaned and came back all good. Hoping someone has had a similar issue and nothing crazy like a cracked block since the motors only have 1600 hours…thanks in advance for any help.

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[Bob Waters]

White smoke can be from low compression or too much fuel.  Rainbow color sheen out the exhaust is bad injector tips.

Try a pressure test on fresh water side of cooling system. Did you change coolant recently? If so, did you burb out the air at top of engine? Loosing coolant is bad. It has to go some where.

What does the exhaust smell like?

I have run these engines and the STP version for 4,000+ hours and never had your issue.

Having 1,600 hours is not the issue, prior maintenance and over propping is a potential problem.

The good thing, the 4LH is a great engine

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