Home » Tony’s Tips » Learning your QSB 5.9 » Your Cummins Marine QSB ThermostatYour Cummins Marine QSB Thermostat This is the housing for your thermostat The view above with the hose removed Thermostat housing fully removed Thermostat A second view of the exposed thermostat, revealing the engine block below. Fully removed, this is the view of your engine block.