My Volvo still has the OEM 140 deg
thermotat installed. (Volvo says leave it even if I switch to fresh water
cooling because all the clearance/tolerances, etc are for SW cooling at 140
deg.)

on some Volvo raw cooled engines the factory specifically recommends against
using cooling water to heat hot water for showers, as this can crack cylinder
heads. Not sure of the dynamics as I do not have a Volvo, but certainly the
man who told me such is one fine mechanic.