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Primer Bulb Size


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I think the primer bulb on my 1999 F115 2 stroke on my 18 redfisher is bad. It currently has a cheapo attwood on and I plan to buy an oem Yamaha bulb. I can't figure out what ID size I need. The main fuel line from the tank to the fuel/water separator says 3/8" ID on the hose. The hose that is attached to the bulb does not say anything on it and I didn't want to cut it off until I had the new one but the line looks smaller. Would there be different size hoses? I emailed SIMs Yamaha and they said stock for my motor is 5/16" (8mm) but the main fuel line is making me second guess. Any help is appreciated!

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SIMs is correct.  Yamaha OEM fuel line is 5/16".  Most people change out to 3/8" cause its easier to find.  I always buy mercury OEM primer balls.  They have two check valves apposed to one in a Yamaha ball.  You can clamp 3/8" fuel line onto a 5/16" barb no problem. 

Also your ball should be before your separator to be able to pull fuel from the tank and fill the separator.  It should also be at an almost vertical position if you can.   



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On ‎3‎/‎10‎/‎2020 at 7:14 AM, Desperado213 said:

So that bulb is set up with 5/16" barbs?


Do you recommend a brand of fuel hose to run from the filter to the motor? Mine is the old gray line and I figured I might as well replace it with the bulb.

Does your grey hose have anything written on it?  It has lasted this long, you may want to buy the same hose again.  There are a lot of different hose brands.  Make sure you buy A1-15 rated hose.  I just used sierra hose on a Jon boat restore.  It was easy to work with and seems good quality. 

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