1972 6hp Johnson wont run unless half-choked

[Wormy_1709]

I have a 1972 6hp Johnson that I bought a while back. It fires right up on the second pull on full choke and after a few seconds of running I ease it to half-choke and it idles up and runs like a champ, but as soon as I take it off choke all the way it dies out. I've rebuilt the fuel pump, checked all the fittings in the hose and tank. I've taken the carb apart and shot Gumout carb cleaner through all the holes, but still no change. What's the proper procedure to cleaning out a carb? When I say I took it apart I just mean I took the bowl off and blew through all the holes. Thanks for any help.

 

[kfa4303]

Re: 1972 6hp Johnson wont run unless half-choked

Hi Wormy. Welcome to iboats. It sounds like you need to rebuild your carb. It's not a big deal. You basically just take it apart, thoroughly clean it, and replace the various gaskets, packings and o-rings. You can get a rebuild kit right here at iboats for about $20. Here are some great links that can walk you through the job.

http://www.leeroysramblings.com/OMC_6hp.htm

http://www.outboard-boat-motor-repa...hnson 5.5 HP 1954-1964 Carburetor Tune-UP.htm

 

[IamCanadian]

Re: 1972 6hp Johnson wont run unless half-choked

Hi Wormy. Welcome to iboats. It sounds like you need to rebuild your carb. It's not a big deal. You basically just take it apart, thoroughly clean it, and replace the various gaskets, packings and o-rings. You can get a rebuild kit right here at iboats for about $20. Here are some great links that can walk you through the job.

http://www.leeroysramblings.com/OMC...hnson 5.5 HP 1954-1964 Carburetor Tune-UP.htm

+1 for that

 

[kbait]

Re: 1972 6hp Johnson wont run unless half-choked

Check low speed circuit passages for clogging. Supply feed on side of bowl must be clear, and needle hole/holes in carb throat, and supply hole on side of carb body(that connects to bowl supply) must be connected..you should be able to blow air (I use a duster can w/straw) into the above mentioned supply port in carb body, and it should pass through the needle hole (needle removed). then put your finger over the needle hole and air should escape from the carb throat holes that feed the motor at low speed. Hope this helps. Oh, and be sure the bowl chamber is vented to atmoshere (top of bowl chamber to one of the holes in front of carb.

Good luck!

 

[F_R]

Re: 1972 6hp Johnson wont run unless half-choked

You can almost bet the farm that the high speed fixed jet ("orifice plug") is dirty. That will cause the exact symptoms you describe. It is in the very bottom of the carb bowl where all the old gas and crud settles. It must be absolutely, positively squeeky CLEAN, with not a trace of dirt or varnish in it. On the other hand, do not go sticking wires and stuff through it. It is a precision hole and damage or oversize is as bad as dirty.

 

[kfa4303]

Re: 1972 6hp Johnson wont run unless half-choked

Now would also be a good time to replace the fuel lines under the cowl as well. It's cheap insurance and the new lines will last for years to come. Just take the ones to the auto parts store and they can cut new ones to length for a few bucks. While you can use regular automotive lines, they do make ethanol-resistant marine fuel lines as well, which are great if you can find them and don't mind the extra expense.

 

[jay_merrill]

Re: 1972 6hp Johnson wont run unless half-choked

You can almost bet the farm that the high speed fixed jet ("orifice plug") is dirty. That will cause the exact symptoms you describe. It is in the very bottom of the carb bowl where all the old gas and crud settles. It must be absolutely, positively squeeky CLEAN, with not a trace of dirt or varnish in it. On the other hand, do not go sticking wires and stuff through it. It is a precision hole and damage or oversize is as bad as dirty.

+1.

A proper carb rebuild must include this.

 

[Wormy_1709]

Re: 1972 6hp Johnson wont run unless half-choked

Ok, so I've taken the carb off and apart and cleaned everything except I cant get the high speed jet (orifice plug) out to clean it. i bought small screwdriver that fit the whole perfectly and I tried screwing it out and it didnt come. I didnt want to try too hard and break anything tho. Is it supposed to just screw out or does it come out some other way? Thanks for the help.

 

[F_R]

Re: 1972 6hp Johnson wont run unless half-choked

Very difficult without the special screwdriver made for the job. It has parallel sides to the blade, not tapered like a regular screwdriver, which will spread the soft brass plug. Once spread, it is almost impossible to remove. Best to just clean it in place. The carburetor cleaners with a dip basket in the can work well for that. Gunk is one brand. Let 'er soak, then rinse with water and blow out..

 

[Wormy_1709]

Re: 1972 6hp Johnson wont run unless half-choked

So unfortunetly I got too inpatient and tried using the screwdriver again before reading the last reply and I dont think I damaged anything, but I may have. I pretty much know I spreaded the brass fitting now. I dont know if it damaged the jet itself because I havnt put it back together and checked everything yet. I have it all soaking in Seafoam and will put it together tomorrow after I blow it all out. Just incase I did damage the jet, if I buy the whole bottom half of the bowl will it come with the jet already in because they said the actually orifice plug is obsolete to buy.

 

[geoffwga1]

Re: 1972 6hp Johnson wont run unless half-choked

I did what you did once with an ev fasttwin.Messed up the screw thingy and then couldn't get it out .Had to ante up and get a whole new carb body,cost $80.Lesson learned.Need I say more?
Geoffwga1

 

[Wormy_1709]

Re: 1972 6hp Johnson wont run unless half-choked

I was able to salvage the carb by taking a torch cleaner and running the smallest one through the jet at the bottom. Come to find out the carb had recently been serviced and whoever did it didnt have the float parallel with the carb housing either. I replaced everything with new stuff from the rebuild kit, made sure the float was level, and put it back together. I just got done installing it on my motor and crank it up and she runs like a top (after a little adjusting with the idle pin). Thanks for all the help. Now im ready for the weekend so I can get her in the water.

 

[kfa4303]

Re: 1972 6hp Johnson wont run unless half-choked

sweeeeet keep us posted on the sea trial. happy boating. vroom-vroom.

 

[jay_merrill]

Re: 1972 6hp Johnson wont run unless half-choked

I'm smiling a boat lovers smile on your behalf - have fun!