1976 6HP Needs 1/3 Choke To Idle ...

This motor was owned by a FD and I doubt it was ever used. It is spotless under the cowling (I hate to subject it to any use, it belongs in Outboard Museum). It runs like a swiss watch at upper RPMs but at idle it stalls out. I took carb apart (didn't take off metal caps) but I did soak it for a long time and thoroughly blew it out. After re-installing, it still doesn't want to idle. If I pull the choke to about 1/3 it idles very well but as soon as you push the choke in you need to rev it up to keep it running. I've adjusted the needle valve from zero to 4 turns and it runs best in the 1 1/2 range.

Could the float be out of adjustment? I did the usual 'level with housing' adjustment but I was wondereing if it can be adjusted to compensate for the engines need for a more 'rich' mixture! If the flow of fuel is based upon a venturi effect perhaps if the float allowed more gas in the bowl, the gas would set higher in the bowl and would be more easily sucked up even thought there is lower vacuum at lower idle.

Re: 1976 6HP Needs 1/3 Choke To Idle ...

i would guess that a complete carb overhaul would correct the issue

Re: 1976 6HP Needs 1/3 Choke To Idle ...

Second that, you probably did not get the idle circuit clean, take the welch plug off and clean the three holes out good with carb cleaner and the wire from a bread wrapper tie; then blow out with compressed air. Hopefully you will be good to go.

Re: 1976 6HP Needs 1/3 Choke To Idle ...

You may also have a vacuum leak would spray foamy water on fuel pump where it bolts to the block and carb to block area while trying to keep it idling and listen for rpm to change. Just a thought

Re: 1976 6HP Needs 1/3 Choke To Idle ...

I'll try a more thorough carb cleaning today but before I do that, I'd like to explore "Marrried_but_not_dead's" comment ("You may also have a vacuum leak would spray foamy water on fuel pump where it bolts to the block and carb to block area while trying to keep it idling and listen for rpm to change").

In the past, I always sprayed a carburetor starting fluid (or spray bottle of mixed gas/oil) when trying to find a vacuum leak (RPMs would increase). "Dead" mentioned using 'foamy water' and I imagine that would also cause a change in the rpm's (a drop in rpm's) but it might also have the advantage of 'bubbling' if it was sprayed onto an area of positive pressure seapage. Hmmm, interesting! Anyone out there use foamy water to detect leaks?

Re: 1976 6HP Needs 1/3 Choke To Idle ...

I have used wd40 or carb cleaner myself......... I save soapy water for my tire leaks

Re: 1976 6HP Needs 1/3 Choke To Idle ...

Your Idle jet is Plugged, use a wire from a Wire Brush and clean it out

Re: 1976 6HP Needs 1/3 Choke To Idle ...

Maybe mine is missing buy I don't see an 'Idle Jet' (see pic below):

#12 is the High Speed Nozzle

#15 is the Slow Speed Needle

I already had the carb apart once and used a fine wire to probe both the High Speed Nozzle, the orifice of the Slow Speed Needle, and all other access holes. I will pull the carb again and remove the Welch Plug and hope that I find something there. My gut tells me I'll give it a thorough cleaning but it will still idle like crap.

It would seem that the depth (or height) of the fuel in the carb's bowl is critical to the operation of the engine, especially at idle when there is less suction due to lower rpms. If I understand the operation of this type of carburetor, the gas/oil is atomized in the open space in the bowl and is sucked upwards as a mist into the high speed nozzle. If this is correct, and this 'vacuumed' fuel feeds both the high and low speeds of the engine, why is it called the 'high speed nozzle'.

As far as I can tell, this (high speed nozzle) is the only exit area of the carb and it feeds both the high speed and low speed circuits! As it enters the nozzle I assume it distributes the atomized fuel in a direction relative to the RPMs of the engine. At slow speed, it detours and passes by the Slow Speed Needle/Orifice and at higher speed it travels more directly into the throat of the carburetor.