Johnson 9 1/2 HP several questions// carb??

It has(had) a knob to adjust R to L on front of motor. What should i set this at? There is no knob which allows it to be turned more than the 3/4 turn range it would have if knob was there. I tried bottoming it out then backing out 1 and 3/4 turns. It coughs, sputters and dies at idle, anything above idle, (2000 rpm plus?) it runs fine. Has new points and plugs, have to start with handle as fast as it will go in nuetral and move it to "shift" position throw it in gear and twist throttle and hope it was fast enough to keep it from dying. Seems even warm it fires right up on one pull with choke pulled out. Also the bulb on fuel line, when I pump it should it stay under pressure? After I pump the bulb it seems to relax to "half tight", other words it needs pumped again to get it to where bulb is non squeezable.

Re: Johnson 9 1/2 HP several questions// carb??

You may find that a small appliance knob with a set screw will work for a knob while you wait for the one from the dealership.

The carburetor, in all likelihood, needs to be rebuilt with a new kit, including the float.

By turning the needle counter clockwise in small 1/8 increments, you should be able to reach a point where the engine will run without continuing to choke it. Then turn it clockwise in 1/8 increments until you get a little cough, stop, turn it back 1/8 and leave it. Between each 1/8 turn adjustment; wait at least 30 seconds for the engine to adjust to your change.

While you are working on the motor, keep the fuel tank as close to level with the engine as possible so that you don't have to expect the fuel pump to violate any laws of physics.

The primer bulb does not stay rigid once fuel is drawn through it, but it should not collapse.

Re: Johnson 9 1/2 HP several questions// carb??

http://www.iboats.com/bbboard/bbBoard.cgi?a=viewthread;fid=28;gtid=818798;gpid=818802

Re: Johnson 9 1/2 HP several questions// carb??

A collapsing bulb means an obstruction between the fuel pickup and bulb, or a problem with ventilation to the tank.

Start with a carb adjustment of about one turn. I agree that it needs a rebuild. But first see if the screws are snug. If they loosen-up, the gasket can leak air in the wrong place and make them imposssible to idle.

Re: Johnson 9 1/2 HP several questions// carb??

It would sound like it's a carburetor problem. But. What year is your 9 1/2? The early ones didn't idle worth crap because of the poor vibration damper design. And they got worse as the vibration damper fell apart. After they changed the vibration damper design, they still had trouble with the upper front rubber mount breaking, which also affects idle. Also, does it run better with the hood off? Those motors have bad problems with smoke inhalation which makes them run lousy. 3rd question, are you running it on a boat or in a barrel? It might be worthwhile to address these questions before tearing into the carb.

Re: Johnson 9 1/2 HP several questions// carb??

F_R said:

It would sound like it's a carburetor problem. But. What year is your 9 1/2? The early ones didn't idle worth crap because of the poor vibration damper design. And they got worse as the vibration damper fell apart. After they changed the vibration damper design, they still had trouble with the upper front rubber mount breaking, which also affects idle. Also, does it run better with the hood off? Those motors have bad problems with smoke inhalation which makes them run lousy. 3rd question, are you running it on a boat or in a barrel? It might be worthwhile to address these questions before tearing into the carb.

Click to expand...

I think it's a 68 but it's been a while since I checked it out. Running right now in a barrell with hood off. I went out and checked the carb screws, a little loose, tightening them it let it idle smoothly at a little lower rpm.
Guess I'll run with the carb rebuild and see what that gets me, I will report back, may be weeks though. My thanks for all replies. Mike