Need help diagnosing outboard running issue.

[Ward H]

Need a little help diagnosing an issue I am having this week with my Yamaha 9.9 4 stroke OB.
New in 2013, it has always ran great. It was serviced and tuned up prior to launch this spring. I only run non ethanol fuel in it. Both times the fuel vent on the tank was open.

Renting a house with a dock for a weeks vacation so brought the boat over from the marina on Saturday.
Yesterday I started it and let it warm up for about 5 minutes. Just as I started to leave the dock, it started running rough, reminded me of a motor running to rich due to the choke being left on. Didn't blow out any blue smoke like I would expect if it was running to rich. I goosed the throttle a few times and squeezed the fuel bulb and it smoothed out and ran fine for the trip out to the bay and back.
Today it ran fine for the run out to the bay and fine for most of the motoring back to the lagoon. Then it did the same sputtering and almost died. Goosing with the throttle had no affect. Squeezing the fuel bulb again seemed to correct the problem, it started running smoothly and continued to do so until docked.

I plan to trouble shoot the issue in the morning so was looking for some suggestions from the group here where I should start.
Fuel Line? Filter?

 

[justsomeguy]

Filters are quick to pull. Air in the line? Check your O rings in the fuel line. Did the fuel bulb feel soft when you squeezed it?

 

[JohnVTX]

I would say fuel filter

 

[capta]

After fuel filter you might check the fuel pump. Sounds like yours has a bad diaphragm.

 

[JRT]

Check those items but also consider the tank vent being an issue. My tank came with some EPA spring preasure valve that didn't open all the time,so I replaced the cap with a manual screw out vent instead.

 

[Ward H]

Did the fuel bulb feel soft when you squeezed it?

I didn't think about it at the time but I believe it did. That would point to bad valve in line? O ring at tank connection? tank vent? tank pickup?

 

[justsomeguy]

I didn't think about it at the time but I believe it did. That would point to bad valve in line? O ring at tank connection? tank vent? tank pickup?

Anywhere along the fuel line after the tank pickup and before the carburetor would be my guess.

 

[DougM]

Pinhole somewhere in the fuel line letting air in?
Still a filter sounds like the logical culprit.

 

[Sailm8]

I had a similar problem with my Tohatsu. Turns out it was the removable fuel line connector like justsomeguy suggested. Motor would run for 2 or 3 minutes as long as I pumped the bulb.

 

[kpgraci]

Modern carbs on today's small outboards have incredibly small ports that are easily blocked with buildup despite how careful you are to keep your gas fresh and ethanol free. I keep a spare carb (a $100 investment) because my Tohatsu 6 routinely fowls with my use pattern, an easy dock side or even open water repair.

As others has said, somewhere between and including fuel tank and carb, but also don't overlook a fresh sparkplug.

 

[agprice22]

First make sure your fuel lines are fully connected. If either end is not fully clipped in, it will result in a soft bulb.

 

[Ward H]

Fuel line was new last September. Tank has a twist to open vent, not spring loaded.
Pulled both connectors, O rings looked good. Coated them with some Vaseline and reconnected.
Ran fine for about an hour while sailing today.
Will be picking up a new filter and fuel line tomorrow. Will replace both if the problem reappears.
If the problem continues after that will have the dealer look at the fuel pump. They won't have time until July anyway.

Thanks for the help.

 

[jibes138]

Try this. I have a Yamaha 20 on a small skiff. It would always start skipping when run at close to full throttle or higher. Then I read that the fuel primer bulb in the fuel line is supposed to be mounted in a vertical orientation. I used a cable tie to hold the fuel hose in a way that the bulb is vertical. No more skipping, it runs great ever since. The check valve in the bulb has the weight of the fuel helping it work when vertical. You may be letting the fuel flow back to the tank if it is laying flat. See post #7 on this link. http://www.marineengine.com/boat-forum/showthread.php?391528-Motor-Losing-Prime

 

[Brian D]

Yamaha had an issue with fuel connectors on their newer models. Mine was a 2011 and in 2013 I got notification that there was a recall on my 9.9 for the fuel connector. Prior to my carburator issues I too had burping issues with fuel. Plus there was a very small fuel leak.

http://www.noonsite.com/Countries/USA/yamaha-outboard-safety-recall
http://yamahaoutboards.com/sites/default/files/modifications/O2014-004R Cust Letter.pdf

I should note that the recall was for the round fuel connector on the motor. Yamaha replaced it with the two prong type connector.