TRACKING DOWN AN OIL LEAK

Q: I have a 2013 Beneteau Oceanis 41 with a 40hp Yanmar diesel. I have it serviced every March (oil, filters and impeller). However, today I noticed about a cup of oil puddled below the engine. I started the engine, ran it in neutral and couldn’t see any oil dripping, but the raw-water cooling exhaust looked like there was a film of oil being discharged. What might be the problem? Robert Weisberg, sailmail@sailmagazine.com

NIGEL CALDER REPLIES

Any time you see oil leaks it is bad news, and a cup of oil is a fair amount! You haven’t specified the engine model and whether or not it has an oil cooler. The oil film in the exhaust suggests it has a cooler with a failing tube, in which case when the engine is running some of the oil is being forced into the raw water system and is exiting via the exhaust, which will cause you to see a loss of oil in the crankcase over time. However, this does not explain the oil puddled below the engine. I confess, I am having trouble fitting these pieces together. Was the oil recently changed? If so, is the puddled oil clean or dirty ( black)? If clean, then likely some was spilled. Other than that, there are a number of places oil can leak out, including a poorly seated oil filter ( which is by far your best hope, as it is cheap and easy to fix whereas most other leaks are not). I would make sure the engine, transmission and pan are spotlessly clean, so that any leaks will be immediately visible, regularly check the oil level in the crankcase, and watch things closely for a while to see if further clues emerge. s