the yamaha engines have many drain passages to allow water to drian out to prevent freezing and to allow sand and debris to drain out as well. These drain passages also allow air to enter teh suction side of the cooling system, thats why V6 yamahas will over heat on the hose, they are sucking air aswell as water and will not pump correctly. Yamaha recomends using the factory hose flush attachement and the flush muffs when running teh engine on the hose. Will your engine pee when the flush attachemnt is hooked up?
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