OldSailor wrote:
I have an old Yanmar 2QM15 - It has a temperature alarm, but no gauge.

Great!

I got a QM30H.

We are in fresh water, so would like
to have engine run hotter - say 160F or so.


Hi:

First questoin ya gotta be able to answere is..........

Fresh water + Coolant in cooling system (like your car)?
or
raw water cooled (engine stays cool by using the liquid that supports
your boat.)?

Then ya got the Sea v. Lake/River (fresh) water choice.

I have read that it may be 120F or 140F
but that's just on web discussions.

Get the book by SELOC titled "Yanmar Diesels 1975-1985" (or someplace
around those dates. Cheep, fast to get, and good enough.

Depending on how your motor is cooled will detrmine the SAFE operating
tempratures.
Bob