Wing engines are notoriously under-operated, under-loaded, and under-maintained, all of which can lead to sudden and catastrophic engine failure. An under-used wing engine may exhibit out-of-spec oil and coolant chemistry, a dry and brittle raw water pump impeller, long expired zincs, and corrosion and pitting of engine internals.
Recommended maintenance on diesel engines calls for run time OR calendar time maintenance intervals, whichever occurs first. Even the most disciplined operators are challenged to run their wing engine more than 25 hours per year. Run time maintenance intervals simply will not provide for the proper care of the engine.
Instead, follow “calendar time” service recommendations for your wing engine by changing engine oil and filter, transmission oil and filter, primary and secondary fuel filters, and the raw water pump impeller at least annually. Check your coolant chemistry using coolant analysis or test strips and recycle stale day tank fuel back to the main tanks. If you haul-out in the winter, change oils in the fall to prevent low pH or moisture-laden oil from wreaking havoc on your engine.
Like any diesel, the wing engine should be operated under load. The engine may not be sufficiently loaded if run in tandem with the main engine so shut down the main and enjoy the quieter wing engine—they work great as trolling motors too!
Three rules for your wing engine: 1) run often; 2) run under load; and, 3) perform maintenance on calendar rather than run-time intervals.