If meticuously cleaning the orifice plug isn’t getting it done….then suggest that he remove the welch plug which exposes the idle system jets…..and meticuously clean that area.

I recently had a 9.5 that was doing exactly that….needed choke to run at idle and was lean-missing all over the place. Was shaking sooooo bad lol….

I could spray carb cleaner through the needle valve opening and I could see it squirting through the three idle holes in the carb throat. I even poked wires through the three holes in the throat….all three holes seemed open and clear from the throat side.

Still ran poorly so I popped the welch plug….cleaned everything from that side….and the problem was fixed. 9.5’s seem to be particularly sensitive to a **very** clean carb.

quote Garry in Tampa:

Those idle cavity welsh plugs come with the tune up kit. I wonder why people are so reluctant to use them. . . 🙄

Well; I am not particularly reluctant to use them; but it has always seemed to me that if I can remove the slow-speed needle and spray carb cleaner through there…..and watch it spray through the three orifices in the carb throat….then that **usually** means that removing the welch plug will reveal a clean cavity. Not always though lol….

BTW….the very late model 9.5’s came with a plastic "filler" that went in behind the welch plug. Can anyone tell me why that was used? What function did it have and if it is an advantage….can the plug be used in the earlier motors? OMC #312909

I assumed (probably wrongly) that it is because the fuel is flowing sideways through that big cavity and could puddle in the bottom of the cavity. With the filler, the cavity is smaller and less room to puddle. On other OMC carbs, the discharge holes are on the bottom of the cavity–self draining, so to speak.