1999 Johnson 9.9/15 hp missing and stalling.

[putzee52]

I posted earlier this year, I have a 1999 Johsnon 9.9 with a dealer installed 15 carb. I bough the boat used and first 2 trips it ran flawless. After that it began stalling at low RPMs. I adjusted the carb misxture screw to level out the idle and fixed, next time out ran funky until i made the adjust again. So i took it back to the marina, they took it apart adjust the idle had it purring like a kitten. Today back to needing an adjustment of the carb screw and it started miss firing. I think im going to install some new plugs, beyond that is there anything else i can check?

Can i put something on the spring loaded screw to stop it from turning and needing adjustment?

Or must i pop the cover every time i tak the boat to the lake?

Other info gas is a good fresh mix once the motor gets rolling it runs well.

Jay

 

[Whoopbass]

Re: 1999 Johnson 9.9/15 hp missing and stalling.

How about setting the idle to where it runs good and then kill the motor. Turn the screw in and count the # of revolutions it takes to screw in snug. (You might be able to mark the screw and somewhere on the carb so you can line it back up perfect). Remove the screw and put some lock tight on it and screw it all the way in and back it out the # of turns and line up the mark.

Are you sure all the other mods were done to your outboard besides the carb change to turn it into a 15 hp motor? A carb change alone won't do it and will cause problems.

 

[OptsyEagle]

Re: 1999 Johnson 9.9/15 hp missing and stalling.

Are you sure the idle adjust screw is moving. Perhaps the fuel is dirty allowing crud into your carb and into the slow speed jet and what your finding is that sometimes when you screw out the needle it temporarily fixes it.

You may need to clean that carburetor and I would also clean the fuel filter and the tank.

All the above is predicated on whether or not your idle screw is moving. If so, fix that first, if not, give my suggestion some thought.

 

[putzee52]

Re: 1999 Johnson 9.9/15 hp missing and stalling.

Im not sure about the idle adjustment screw turning, i do know a small adjustment to that screw allows the motor to run flawless.

As for the carb, i know it was dealer installed when the local lake had increased it's hp limit, the previous owner wanted a little more power for no a lot o money.

The fuel filter was cleaned and the last tanks of gas i ran with seafoam clener in the mix.

One other thing i had noticed was the motor spits out some crusty deposits that dissapate into an oily film, it looks like a calcium build up but comes from the prop area.


Now for the newby to boats question. My throttle comtrol is an OMC, what is the knob like thing below the key?
Jay

 

[CanadianEh]

Re: 1999 Johnson 9.9/15 hp missing and stalling.

The knob is your friction adjustment for the throttle lever.

 

[the machinist]

Re: 1999 Johnson 9.9/15 hp missing and stalling.

Sounds to me like slight debris in the fuel/carburetor & when it misses, you adjust the idle jet, it allows the debris to become dislodged & it runs until next time.

As CanadianE said, that idle adjustment screw should not move as all I have seen have a spring under the head to keep it from moving.