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1984 Mariner 9.9C Fuel Problem

C

cchildr84

New member
I have a 1984 Mariner 9.9C outboard motor that I am having problems with. When I have the fuel line connected it doesn't want to idle or rev up correctly and tends to bog down. However, when I remove the fuel line and it is only running on the fuel that is in the carb bowl it idles and revs up as it should. I have put a new carb rebuild kit in it, and the primer bulb will get hard as it should. Also, I can rule out the fuel line, primer, tank, etc. as I use it on another motor and it works fine. With that said, my inclination is that my problem is in the fuel pump, which I have not rebuilt or replaced any parts. Would you all agree that my problem is with the fuel pump or are there any other thoughts. Your help is appreciated as I love this motor and really want to get it back running right. It has always treated me right, so I want to treat it right. LOL.

Thanks,

CCHILDR84
 
Likely need a new diaphragm in the pump.----------The majority of folks will buy a new pump instead of learning how easy that repair is.
 
If that is the yamaha built motor be very careful taking the fuel line off the pump,the plastic spacer gets brittle and you can break off the nipple. I don't know of any aftermarket parts for that carb so you will need the dealers help. Hopefully a carb kit is available otherwise you will have to buy it piece by piece.
 
flyingscott said:
If that is the yamaha built motor be very careful taking the fuel line off the pump,the plastic spacer gets brittle and you can break off the nipple. I don't know of any aftermarket parts for that carb so you will need the dealers help. Hopefully a carb kit is available otherwise you will have to buy it piece by piece.
Click to expand...

It is indeed one of the Japanese made Yamaha Marines. The plastic spacer is in pretty good shape. I believe I will try to replace the diaphragms and see if that fixes my problem.
 
Ok, so I replaced all of the diaphragm's this weekend and it was still having the same problem. When the fuel line was connected to the motor it would bogg down. Without it connected it ran as it should while running on only the fuel in the carb bowl. So I'm puzzled as to the problem. There was some fuel coming out of the top of the carb. On a side note I checked the high speed jet and it was clean, but when I put it back in I broke it. I can get a new one through Yamaha. Does anyone know whether or not the high speed jet is an adjustable or non adjustable jet. Do you just set it in snug and call it a day?
 
It's flooding!

Lower the float level a 1/16 inch at a time until it stops. Using my test tank, I clamp the carb in a vise and pump the bulb rock hard. Much easier that way.

Jeff
 
fastjeff said:
It's flooding!

Lower the float level a 1/16 inch at a time until it stops. Using my test tank, I clamp the carb in a vise and pump the bulb rock hard. Much easier that way.

Jeff
Click to expand...

Is the adjustment made by loosening the valve seat? I don't see any other way of adjusting the float arm.
 
fastjeff said:
Plastic float? Usually there's something metal you can bend.

Jeff
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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.
 
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