I change once a year as a minimum. In addition, I try to change every
hundred hours, and its nice to do an extra change towards the end of
the season, so it sits over the winter with clean oil. The result of
all this for me is one change in the spring after launch, an usually
one in the fall when I return from my last trip.

IIRC, my manual advices every 150 hours.

Steve wrote:
I know this question has come up in years past but I'll ask it again.

My diesel (Volvo MD2B) now has about 200 hrs and I changed the oil at 50
hrs. I changed it again yesterday, just because it had been over a year
since the last oil change.

Beyond the 50 hr break-in oil change recommendation, I find no further
guidance in the owners manual.

What is the normal change frequency for a sail boat aux. engine when it is
in frequent use. (cruising with daily operation)??

FWIW. I'm using Shell Rotella-T 15w40 and change the filter each time.

Thanks,

Steve
s/v Good Intentions