I've got a 2014 Mercury 9.9 4 stroke I bought used last fall.

Prior owner said he ran regular 87 octane with ethanol gas in it. I did an oil change and lower unit gear oil change as soon as I got it home.

I have been using 91 octane no ethanol. It fires right up on the first pull after sitting for a couple weeks, I disconnect the fuel tank line and don't run the outboard out of fuel when I leave the boat ramp.

The last 2 trips out I've had an issue with it stalling after rolling off from full throttle to slow for a fishing spot/dock. It with stumble then die. It fires right back up and takes off. But I think its not running up to its full potential in general, I think it was more loud earlier in the year.

I'm planning on doing new plugs first, then a carb rebuild if plugs don't remedy it.

Anyone experienced this issue?

Fuel pump ?

Pump the fuel line bulb, while twisting the throttle.
See if it improves.

Throttle tip in with a stall is usually a lack of fuel from idle circuit to primary circuit.


As it transitions it goes way lean enough to stall it out.

Figure out why.

Main jet is partially plugged. When you accelerate, it leans out and would be the first place it would show up. A bit more and it'll start causing issue at a steady loaded RPM.

Sitting and not running, especially with ethanol gas is bad on the carburetor. My friend runs 100% gas and had to replace the carb last year on the same year motor, but we also use it in a saltwater environment one a year.

Also if you store the motor off the boat make sure to lay it down on the correct side.

Pilot jet (idle jet) probably obstructed.

#10 in this diagram.

Attached File


#12 is the main jet.

The holes in the idle jet and emulsion tube, #9, are so tiny and they all

must be spotless. This engine type runs extremely lean at idle and any restriction in any of the

jets or passages will cause issues.

<-- Maintains a fleet of these engines.

ETA - All passages in the carb must be spotless, not just the jets/e-tube.

Carb buy an ultra sonic cleaner.

A big thank you for that diagram. And thanks to everyone else who chimed in.

Any recommendations on where to get a factory service manual for the 9.9? I want to replace the water impeller at the end of the season.

It's stupidly easy, you don't need a manual and if you need any help, there are plenty of vid's on the net to help you.

The hardest part is making sure you unhook the shift linkage under the engine cover and that's not hard, it's just you need to know to do it.

Cool.

Anyone care to share their go-to website for ordering Mercury outboard parts?

Boats.net.

Locally, most any mercury dealer will have the impellers in stock, they are $12-$15 or so for that size. I just did my 6hp Mercury a few weeks ago. The carb rebuild kit I ordered from Boats.net.

Shift linkage is disconnected via a threaded coupler just above the lower unit. You must also remove

the little plastic "catch" that is used for the reverse lock. This plastic catch is held with a screw. The catch

is brittle so be careful with it.