1985 Mercury 9.9 2 stroke won't start, Please Help!!!!!

[Tablowe1457]

As the title states I have a 1985 Mercury 9.9 2 stroke that will not start. A brief history I bought the motor used and it ran great at the guys house. I tried it at mine and it started first pull ! So I decided to give it a couple full throttle pulls. On the last one it broke up and stalled. This is were my predicament begins. It will not start on choke when cold. the only way I can get it to run is too hold the throttle wide open and when this is done it will start but will not idle at all. Will just run from about half throttle and above. Has great spark, 95 psi of compression both cylinders, the key way on the crank isn't sheared, brand new fuel tank with premium fuel mixed 50:1 and the carb is clean as a whistle. I don't get it please help!!!!

 

[flyingscott]

Need a serial# not sure if merc made a 9.9 in 1985

 

[Tablowe1457]

Hi thank you for answereing, the serial # is 0A947111

 

[ondarvr]

You should never rev the motor that high when it's not in the water under load, bad things can happen.

Clean the carbs, it will need that done no matter what the issue is. Premium fuel is of no value, save your money.

 

[Tablowe1457]

The motor is in a barrel of water at the proper level on a stand everytime i have messed with it. I have already disassembled and cleaned the carb.

 

[ondarvr]

The wiring on some older Mercs tends to get brittle and crack, which may lead to wires shorting out, check to see if that's an issues with yours.

And if this year has a kill button on the tiller handle they can short out where the tiller hinges.

 

[Tablowe1457]

Yes i had thought the same thing,and checked that, but the wiring is fine. But im pretty sure if this was the case it wouldnt start at all. This motor will run from part throttle up to wot no problem. It doesnt start unless the throttle is manually moved by hand to part throttle and it will not idle.

 

[CharlieB]

It doesn't take much to clog the idle circuit in those small motors. If it runs on the main jet but starves and dies near idle then it is a good indication it isn't passing fuel. You can test this with a window washer spray bottle of pre-mixed fuel, squirting a bit into the carb as you bring the idle speed down. If you can keep it running but it dies when you stop then you pretty much prove the carb at fault.