1999 Volvo Penta "WT" Models Workshop Manual, Page 346Get this manual
Draining Supply PumpV6 and V8 Models Only _
1Loosen and slide hose clamps backRemove hoses from the pump and drain
2Crank the engine no more than seconds (DO NOT START) to expel any water trapped in water pumpReattach hoses
Thermostat Replacement
3.0 GS Models
1Remove all hoses