I have a 9.9 yamaha fours stroke. In the last month it has started loosing prime while running. about every half hour to 45 minutes it will start sputtering and ill have to pump the primer bulb then itd good for another half hour 45 minutes. any ideas I could check myself before taking it in.

thanks to all

Gary

Check the primer bulb for a pin hole. I had the same thing happen a couple of years ago and the hole was VERY small . It took a while but it let in enough air to loose prime. $10 for a new bulb and ... problem solved. Maybe you'll get lucky with a cheap fix.

It could be the volatility of modern gasoline, if it only happens in hot weather. OB engines suck the fuel from a lower tank, cars and trucks have electric fuel pumps in the tank, so the fuel line is always pressurized. With an OB, the fuel line is under a slight vacuum.

I have a 9.9 yamaha fours stroke. In the last month it has started loosing prime while running. about every half hour to 45 minutes it will start sputtering and ill have to pump the primer bulb then itd good for another half hour 45 minutes. any ideas I could check myself before taking it in.

thanks to all

Gary

Gary... What year?
The late 90's - T-9.9 models, all liked to do that.
If yours is of that vintage, the fuel pump could be the problem.
We dealt with it for years.
Yamaha would never admit anything was wrong...;) but.... they did come out with a water cooled fuel pump...which solved our problem. :)

PS... this Yamaha water cooled fuel pump bolts right up on a Merc 9.9 Pro-Kicker, too.... if you get my drift...;)

Tmac you couldnt happen to know a part number on that would you? I have tried to find that with no luck.
Thanks

Yep Mine is a 1999 High thrust Four stroke. so if you do have that part number it would be great i did put a new primer bulb on but have not got to try it yet.

Thanks foir all the help guys

Gary

I've seen a fuel pump exhibit the same symptoms on a late 90's Evinrude 9.9 kicker as well. Not sure about the Yammie, but it was pretty easy to change on the Rude.

Tmac you couldnt happen to know a part number on that would you? I have tried to find that with no luck.
Thanks


No... since I am now retired... I don't have access to part #s.
Most Yamaha parts managers would know, 'tho.