Yamaha, Y15 SMHA 2017

by John Lawson
(Port Orchard, Washington State, USA)

Won't Idle Low For First 15 Minutes


Hi, I've got a 2017 Y15 SMHA outboard that has trouble starting (4th or 10th pull).

Once it does start, it stalls at low idle. I have to fully gas it for 15 minutes before it will be stable at low idle.

Once it warms up, it has no trouble, but if I shut down the engine and it sits for 3 hours then the issue returns, even in warm weather.

This is only really a problem because the outboard only goes into gear when it's in low idle, so I can’t even drive the darn thing while it’s warming.

Weather here in the Sound has been 50 Degrees F.

History:
I got this outboard in March, the PO warned me the motor took some time to warm up, but this is kinda silly. Said he’d been running it all winter.

Notes:
* Yes, I'm starting the outboard in the throttle starting position, and I've tried every other throttle position just for fun.
* Yes, the rumors are true; this outboard doesn't have a manual choke. No, I'm not missing it, the engine has a Yamaha Primestart system.

Things I've tried:
* Pulled and tested the Primestart valve on 12 volts. It works.
* Running 100% ethanol free gas
* Seafoam fuel system cleaner
* Replaced all fuel lines & fuel bulb
* Checked for fuel leaks - none
* Replaced inboard fuel filter and axillary racore water-fuel filter
* Carburetor rebuild * clean, complete with meticulous scrubbing & air hose blowout, jets were not blocked when I took the carb apart
* Visually checked all relevant gaskets – they look good
* Checked for Vacuum leaks - nothing
* Pulled and cleaned spark plugs, checked for gap and spark – all good
* Visual inspection of air filter – clean as a whistle
* Read every damn forum post I could find, called three mechanics, and spent days working on the darn thing
* When I store the outboard at the end of the day, I always shut off fuel and let the carb run dry

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