Volvo Penta Thermostat.
Your thermostat is an intergral part of the cooling system and should be checked regularly for correct operation. Coolant should be changed, preferably with ready mixed, every 2 years and the the heat exchanger removed for cleaning every 5 years.
Volvo Penta Part No: 3580365
For Volvo Penta Diesel Engines: D2-55A, D2-55B, MD2030, MD2030A, MD2030B, MD2030C, MD2030D, MD2040, MD2040A, MD2040C, MD2040D