2003 Yamaha F115 4 stroke Vapor Lock?

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CR Angler

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Jun 3, 2016
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Motor stars easily after priming and idles/runs slowly with no problems. Throttles up and runs smoothly on plane. After 1/2 hr or more, I shut it down to fish for 1/2 hr or more then idle a few minutes to deep water. Throttle up to plane. Everything fine for 2 or. 3 minutes whereupon motor coughs and acts as if fuel was disconnected. If I pull throttle back quickly, motor idles normally. If not, it quits. After pumping bulb, motor starts immediately and runs normally - high speed, idle, mid range, etc until I turn it off. Seems to be happening now every time motor is shut down for 1/2 hr or more. Water indicator stream is strong.
Motor has 532 hrs.
Spring maintenance included new plugs, water separater, thermostat check, new fuel filter on motor (red ring is at bottom). Since having this prob I have checked fuel tube in tank (screen at bottom clean), new anti-siphon valve, new fuel hose all the way to motor, new water sep. filter.
Prob only seems to occur after motor is hot is shut down for a while. Once bulb is pumped - no more prob.
If anyone has experienced this, I'd be grateful to know the fix.
 

19 Fathoms

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Jun 27, 2019
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Did you ever get the answer to your problem? I have the same motor (F115TXRB) with about 330 hours on it and the same problem. I'm a retired certified Mercury Marine Outboard / Stern Drive mechanic and dealer and I've had the entire fuel system apart, cleaned it, replaced any suspicious parts and adjusted, but still the problem persists. Some trips no problems, sometimes it happens once and sometimes 4 or 5 times. Never had this problem (vapor lock) with the Mercs.
 
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