I never used the engine blower for my Yanmar 4JH. I always thought that a diesel engine needs plenty of fresh air, and to suck air out of a tight engine compartment never seemed like a good idea to me. Until I started having overheating problems with the Balmar alternator. I reversed the flow on the blower to pump cool air into the engine compartment, directed at the alternator. Result: a cooler alternator and plenty of fresh air for the engine.