My Seloc repair manual for my 1997 Volvo Penta 4.3L with and SX outdrive
says the engine takes a 160F thermostat. That is what I installed in
spring.

The mechanic who worked on my boat after the overheating incident says it
takes a 140F thermostat and that is what he installed.

Does anyone know the correct thermostat temperature rating for this engine?

Will running the wrong thermostat temp have a negative effect on the
engine's performance?

TIA!