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post #1 of 9 Old 06-21-2007 Thread Starter
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mysteries of outboard motor behavior

Here's a newbie question for y'all:
I have a 9.9 hp Yamaha outboard on my boat. I recently replaced the fuel line with squeeze bulb to resolve a no-start problem. Now it starts every time with the push of a button! Then it runs for 10-20 minutes with no problems, then it dies. At which point I open the locker and squeeze the bulb a few times and then it starts right up again and runs for 10-20 minutes and then dies. Repeat...
So, why does it do this?
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post #2 of 9 Old 06-21-2007
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Mmmm...Did you open the vent screw on the fuel tank? (Don't ask me why I know this.)

Any pinholes or cracks in the fuel line or conenctions, that are letting air get into the line and breaking the suction to the fuel?
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post #3 of 9 Old 06-21-2007
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Second the idea of the vent, or possible air leaks...
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post #4 of 9 Old 06-21-2007
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Check the filter(screen) on the inside of the tank.
Sounds like it might be plugged up.
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post #5 of 9 Old 06-21-2007
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If you have opened the vent, then my guess it is the carburetor or the fuel filter. Another possibility is that you have an air leak in the fuel like... a common place for this to happen is the banjo bolts in the fuel line.

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post #6 of 9 Old 06-23-2007 Thread Starter
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Thumbs up thanks

Thanks, everyone. This forum is a great resource. Yes, the vent cap is open while motor is running. I will check for possible air leaks, clean the intake screen, and replace the fuel filter.
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post #7 of 9 Old 06-23-2007
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Although with it restarting so quickly it does not seem likely that it could be overheating, but is the waterpump working?
Also when you squeeze the bulb is it hard?
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post #8 of 9 Old 06-23-2007
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It may also be a bad fuel pump, but I would bet on a bad quick-connection first.
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post #9 of 9 Old 06-23-2007
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Did you do any maintenance on the engine prior to this recent bout of usage? If so, did you touch the fuel lines in anyway.... if so, likely you overtightened a banjo bolt and mangled the copper washer, and it will leak air.

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