84 Mariner 9.9C Carb Issues

[cchildr84]

Ok, so I tried taking my motor out on the lake this weekend, and had no luck. It turned over for a little while but then died out. Got home and it appears that it was flooding out. Now the primer bulb on the fuel line was hard. Fuel was coming back out of the carburetor into the air box. Do you think the needle is sticking or what would cause it to do that? Prior to going to the lake I had it running in my drive way, but it wasn't idling very well. From a seated position I turned the idle screw 1 1/2 turns. From there no matter which way I adjusted it, it would idle right and wanted to cut out when I idled down on the throttle. Your help is appreciated. I really want to get this motor back to running right. It has always been a reliable motor, it has perfect compression at 120 psi in each cylinder, but for the life of me I can't get this fuel problem straightened out.

 

[mfkadz]

The first thought is a stuck carb float. That would dump gas all the time. But it sounds like the bulb is hard. If you pump on the bulb do you see fuel going into the carb throat? Another bad thought is a reed is not seating correctly and your getting blowback from the piston.

mike

 

[cchildr84]

Ok, so it's been a long time since I've messed around with the motor to look into this carb issue further, but finally played around with it a little more this weekend. So it's still doing the same thing while running fuel will start leaking from and backing up into the air box. However, if I pull the fuel line from the motor and let it run on only the fuel in the bowl it will idle down correctly and rev up as it should. As soon as I put the fuel line back on it starts to want to flood out again. So with that in mind I feel fairly certain the issue is in the carburetor. Do you guys think the fuel pump is bad and is letting in to much fuel in? What are y'alls thoughts?

 

[cchildr84]

Ok, a long overdue update. I replaced all of the diaphragm's in the fuel pump this weekend and I'm still having the same problem. It wants to bogg down when the fuel line is connected. But again when it's just running on the fuel in the carb bowl it runs as it should. I puzzled as to the issue. The needle valve is setting properly and the primer bulb gets hard. How would I determine if a reed leaf isn't setting properly. Also, I took the carb back off and checked the pilot/high speed jet and when I put it back in, tightened it a bit to much. Luckily since this motor/carb was made by Yamaha I can still get a new jet. Does anyone know if this is a non adjustable pilot jet or know hw to tell if it is adjustable or not? Your help is greatly appreciated. I'm determined to get this motor back to running properly. It's to good of a motor to give up on.

 

[cchildr84]

So I'm thinking the valve needle is to short. When I read the manual, it states once the needle and float arm are installed the float arm should be 0.078in +/- 0.02in above or below the float chamber packing seat. In order for the valve to cut off fuel supply it goes way beyond that. Now I've ordered two carb kits for this thing and continue to have this same problem. I ordered the kits searching under mariner part numbers. The kit number I have is 84473T. I haven't tried ordering a kit through Yamaha; part #677-W0093-04-00, but in looking at the pictures the needle looks to be the same length. My carb is stamped 6E770. Is there a possibility that the needle is to short and not shutting off fuel, and if so can someone direct me to the right part #. When it starts flooding out, fuel starts to spew out of the bypass chamber in the carb; as an added note.