Yamaha 4hp 2 stroke outboard intermittent no start problem

ajf10

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Nov 26, 2007
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3
I have a 1992 yamaha 4q 4hp 2 stroke outboard which I use on a small inflatable dinghy that I tow behind my sailboat. After transporting the engine horizontially in the car for a short trip, or after towing the dinghy with the engine on it for a relatively short boat trip, the engine will sometimes not start. When it has been sitting still and upright for some time, such as on the stand in the garage, it will start up, usually on the first try. It runs well when I am able to start it.

I am not sure where to look for trouble. The engine has a built in tank and a fuel cut off switch at the bottom of the tank which connects to a short length of fuel line to the carb.

Is it possible that the carb is flooded due to fuel from the fuel line when the engine is lying on its side in the car, or bouncing around while being towed in the dinghy? I have been shutting off the cut off switch before transport but there is still some fuel in the line between the cut off and carb.

My other thought was that air is getting in to the fuel line in transport, and since there is no primer bulb I can't pump it out.

The fuel is relatively fresh, about a month old, the oil is carefully measured prior to mixing, and I have been using an ethanol treatment.

Thanks for your help!
 

ajf10

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Nov 26, 2007
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3
Re: Yamaha 4hp 2 stroke outboard intermittent no start problem

Bump, thanks
 

99yam40

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Sep 7, 2008
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9,241
Re: Yamaha 4hp 2 stroke outboard intermittent no start problem

I would think that the fuel in the carb would drain out when laid down,and possibly tilted up and bouncing also.
You may try draining carb bowl after shutting off fuel line to see if that will help keep it from flooding the motor. The tank will try to pressurize if not vented as fuel is sloshed around
 
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