Recently we have come across foaming in used marine engine oil SAE 40 after 5300 hrs of usage and the UOA says that the
Pentane Insolubles is 1.13
Mositure content is 0.0917%
Viscosity & flash point are under limits.

We had checked the engine for air leaks, blowby and lube oil line leaks and found no evidence of leakage.

Could anyone relate to this problem and suggest some preventive measures.

Franky,

How do you checked Engine for Oil Leaks?
What is the FTIR Oxidation Level?
What is the Engine oil Pressure?
Sounds Pentane Insoluble is quite high.
Perform Wear element analysis.

Regards

Bala.