Volvo Penta has a long history of successful marine engine design. Their multiple cylinder engines can be found on many of today's pleasure craft and fishing boats. The water pump on the Volvo Penta has an external mounting at the front of the engine, easily accessible for the average repair person. Replacing the water pump impeller constitutes one of the major repair and maintenance procedures on a Volvo Penta engine. With no external housings that must be removed, the water pump can be replaced within an hour with a few steps and basic tools.
Unclasp the clamps on the engine cover and pull it off the engine. Locate the tensioner pulley, identified by a large nut in the centre of it, to relieve pressure on the serpentine belt. Place a socket and a breaker bar on the pulley nut. Turn the breaker bar downward against the spring pressure and slip off the serpentine belt. Note the routing configuration of the belt before pulling it off.
Place a drain pan directly under the water pump -- the water pump mounts to the outside of the crankshaft pulley, low on the front of the engine. Use a screwdriver to loosen the inlet and outlet hoses on the water pump. Remember which hose goes to which neck fitting. Let the coolant drain into the pan. Push the hoses aside.
Use a socket to remove the two bolts that hold the bracket to the water pump housing then set the bracket aside. Use a large slotted screwdriver to loosen and remove the four screws that hold the water pump to the pulley. If they are frozen in place, spray penetrating oil on the screws and let them soak. After removing the water pump, turn it upside down. Remove the circular ring gasket from its groove. Clean the housing surface with carburettor cleaner and a gasket scraper, along with the mating surface on the pulley.
Look at the impeller inside the water pump and notice which way the rubber blades point. You need to install the new impeller in the same configuration. Pull the impeller out of the water pump housing. Gently sand the inside of the impeller chamber with 400-grit sandpaper. Remove all scale, burrs and debris. Clean it with carburettor cleaner and a rag. Place the new impeller inside the chamber, orienting the blades in the proper direction.
Place a new gasket ring in the groove on the housing. Push the gasket ring firmly in place to seat it. Align the water pump up to the pulley and start the screws in by hand. Finish tightening the screws with the slotted screwdriver. Push the inlet and outlet houses back onto the water pump nozzle necks. Tighten the hose clamps with the screwdriver. Place the water pump bracket back into position. Insert the two bracket bolts and tighten them with the socket.
Run the serpentine belt back through the pulley system. Place the breaker bar and socket onto the tensioner pulley and push the breaker bar down. Slip the serpentine belt back onto the tensioner pulley and release pressure on the breaker bar. Remove the drain pan. Fill the coolant system. Replace the engine cover and snap the clips back into place.