Yamaha 115 outboard - runs all day - then won't start

dicarlo

Seaman Apprentice
Joined
Nov 14, 2012
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34
Have a 2004 yamaha 115hp 4 stroke. The problem started this summer. Primer bulb gets hard, it'll start and run all day, until shut off. Then won't start until it sits for an hour or more. Has new fuel filter and vst filter, and water fuel separator was done summer 2016.

When it won't start, it fires like it's starting but that's it. Possible air in the line somehow that is occurring once I turn the motor off?
 

alldodge

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Mar 8, 2009
Messages
40,582
Have a 2004 yamaha 115hp 4 stroke. The problem started this summer. Primer bulb gets hard, it'll start and run all day, until shut off. Then won't start until it sits for an hour or more. Has new fuel filter and vst filter, and water fuel separator was done summer 2016.

When it won't start, it fires like it's starting but that's it. Possible air in the line somehow that is occurring once I turn the motor off?

I see the VST as it just may be your issue. Not a Yam guy but the VST's on all motors have been an issue (my experience is inboards). The reasoning is the fuel is getting hot and starts to boil. The boiling creates an air pocket in the fuel rail and when cranked no fuel makes it thru the injectors. With inboards this happens after sitting for an hour or two. I'm guessing is the cool down time is lessened because of it being an OB.

The fix for inboards is to run the blowers longer before turning the motor OFF, and even open the cover for more air.

Does this happen right after shutting it down or take a bit longer?
 
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