Have a regular cooling water temp gauge, and it has never been above 175F.
Note: The Volvo Penta Gas engine oil is 15w50 and API SG.
I have access to diesel oil with the following grade:
API CI-4/SJ, ACEA E7/E5/E3/B3, MB 228.3, Volvo VDS 3, MAN 3275, Allison C-4.