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motor problems

1886 Views 13 Replies 8 Participants Last post by  endevour
i have 20 horse power yanmar 3GMF motor. in neutral i can get the rpms up to 3500-4000 if i wanted, however when i put it into gear the highest i can go is about 2000. when i go above that i get heavy black smoke from the aft thru hull. no smoke in cabin or engine compartment. is this an exhaust mainfold problem or maybe a saltwater cooling problem? thank you for any help you can give.
1 - 1 of 14 Posts
you should not be getting black smoke under load. your engine is overloaded. you may have a line wrapped around the prop, bent blades, some other drag. i don't think it is a plugged up air cleaner because you can get up to high RPM in neutral. is the engine overheating?
1 - 1 of 14 Posts
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