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strange behavior

D

Doug2104

New member
I have a 40 HP, 3 cylinder, 2 cycle Yamaha.

Boat goes well. Then slows down by itself. I ease off on the gas and when running very slowly there is a noticeable kick and it runs well again. This action often repeats.
 
fresh gas? no water in gas?vent on tank open and working?does it fail if someone is pumping the bulb?
 
Fuel flow restriction somewhere. Your diaphram pump can fill the carbs with fuel and she'll run strong until the carbs are drained then she chokes and is fuel starved... throttle back and the carbs fill again ready for another push until that fuel is burned off. Check adn change all filters you have along the way and remember there may be a filter on the fuel pick-up line that sits on the bottom of your gas tank that is clogged. Many don't know that before the Racor filter (if you have one), before the under cowling filter and all the others that may be in line beyond that... there may be that stupid filter on your tank pick-up line installed by the boat manufacturer purely for warranty reasons in case they left some crap in the tank when it left the factory. If there is a filter on that pick-up... pull it off and throw it away as it never should have been put there and is not needed with all the other filters along the way.
 
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