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post #1 of 2 Old 05-12-2013 Thread Starter
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help seating a diaphragm

My carb from the side.

I believe, but am not sure, that this part is the accelerator pump.

The inside looks just like this

Their is a diaphragm, metal in the center, that sits on a spring.

Lat year, the motor ran rough, so I brought it into a good shop, and it ran great. Until I let it sit a couple of weeks. (Thank you ethanol) The boat was on the water, so I pulled the carb, and brought it to a different, but equally reputable shop.

On the last day of the season, I put the carb on, and the motor started instantly and ran great. But, it leaked fuel like a sieve. I brought the carb back to the shop, and just picked it up this week. They had replaced the accelerator pump diaphragm.

I put it back on, and it still leaks. While I am sure the shop will stand behind their work, it is 1.5 hrs from my house. And, at this point, they may need to see it on the motor while it is leaking. They really shouldn't. It is possible to reproduce this leak by pumping fuel into the carb, then doing the equivalent of hitting the throttle. I really don't want to remove a motor and make 2 three hour round trips to fix this.

I have tried to reseat the diaphragm, but it keeps leaking. There must be some kind of trick. Anybody know the trick?
meboater is offline  
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post #2 of 2 Old 05-12-2013
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Re: help seating a diaphragm

Looks like a carb from the sometimes over-rated Yamaha 9.9

I've had the same problem with mine. Or should I say, this is just one of many problems. I can offer two solutions: 1., as you seat the cover back down with the two screws pay close attention to where the brass center is. Look through the small gap as you tighten the screws. Hopefully the diaphragm hasn't already been damaged; if so, order another from an online vendor of your choice. 2., give the repair shop a call and, if they approve, mail the carb to them with return postage paid. Either way, good luck.
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