1998 Mercury / Mariner / Yamaha 9.9 carb problem fix

[-JR-]

For those that have a 9.9 Mercury / Mariner/ Yamaha that have these electronic valve sitting on top of the carb that fail . (Engine hard starting etc.) you can take off this part and test it with 12 volt battery and if it does not pull in in 5 minutes it is no good.
The power coming off the engine to the valve is around 6 volts A/C and increases with more throttle .
Price for a new one is around $100. how long will it last ?
My fix was to cut off the little piston valve from the electronic side and cut off the wires and place it back on the carb with rubber seal. If you get any air leak it will not start.
Tape up those supply power wires and and leave them alone on the engine.
Engine started just fine after this fix.

Not really sure if it is a choke or emission item added . They are just junk.
Now it runs like a Merc!

JR

 

[MH Hawker]

Re: 1998 Mercury / Mariner / Yamaha 9.9 carb problem fix

Interesting, that is the electric en-richer for remote starting, it has 2 one on the top and one on the side that is for manual starting. The little hole the rubber tipped plunger piston covers when its starting is to make it pull in more fuel on a cold or hard start, The one on mine was original to the motor and its a 1996 that fell apart on a long trip and I did have to replace it last year, but no problems since. How ever if you have plugged off the little hole to get it to run or start then you have some other issue. On that motor how the mixture screw is set governs how easy the motor will start. If its to lean it is very hard starting if at all. I suspect you have it set way to lean.

 

[-JR-]

Re: 1998 Mercury / Mariner / Yamaha 9.9 carb problem fix

The air mixture screw on this carb has a steal plug capping it. Manual says unadjustable. I hate to try and pull the plug and find no screw Might be opening a can of worms trying to reseal that hole.
May be what you are saying is right leaving that hole open will run rich,she might pull like a 15 hp unit now.
Only using it as a kicker in case the main engine fails in the middle of a lake.

 

[MH Hawker]

Re: 1998 Mercury / Mariner / Yamaha 9.9 carb problem fix

The hole is suposto be left open, when the sel is engaged the rubber tip covers the hole and causes it to draw more fuel into the carb like a manual choke used to do on the older motors. How ever if the mixture screw is non adjustable, and its running ok I would run it as is. It is adjustable on mine but its a 2 stroke.