1999 Volvo Penta "WT" Models Workshop Manual, Page 334Get this manual
Description
Water is supplied to the engine by means of an impeller type pump (supply pump)The water supply pump is mounted on the engineWater supplied to the engine is circulated in the engine by means of centrifugal type pump (circulating pump),
The supply pump used on 3.0 GS models is self priming impeller type pump, mounted on the engine and belt drivenAll V6 and V8 models use crankshaft mounted pumpDuring low speed operation the impelierfunctions as positive displacement pumpAt higher speeds it functions as combination centrifugal and positive displacement pump