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Old Johnson Outboard carburetor adjustment

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oldangler

New member
I recently acquired an 25 year old, 30 HP, 2 stroke Johnson outboard tiller. It was hardly used by the previous owner and it sat in a shed for years. I had it tuned up, new plugs, wiring, carb kit, etc. The compression is 145 in both cylinders. My problem is when I run it I have to have the primer knob partly out - showing some red. If I push the primer all the way in once it is warmed up, the motor loses power and RPM`s. It appears to me to be running to rich. The boat shop said they had adjusted the carburetor and idle. I`m several hours away from the shop and didn`t want to drag it back there. I`m not a mechanic but if someone can help me try to make some adjustment, that would be great. Otherwise I will haul it back to the service shop.
 
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I agree it is running too lean thats why you need to crack the primer. What that does is pump fuel directly into the manifold. Did you try adjusting the slow needle on the carb?
 
Thanks to everyone who replied to my post.

I fooled around with it for quite awhile with no improvement before hauling the boat back to the shop. The tech took the carb off again and didn't find anything so put it back together and ran it in their tank. It ran OK, I picked it up several days later with N/C on the work order. Its been running pretty good, it idles good and also runs well at full speed. I've been adding a bit of Seafoam to every fuel up since the problem.

I still think I sense a bit of a hesitation when you throttle up so I'm wondering if I should replace the fuel pump? Any suggestions
 
oldangler said:
I recently acquired an 25 year old, 30 HP, 2 stroke Johnson outboard tiller. It was hardly used by the previous owner and it sat in a shed for years. I had it tuned up, new plugs, wiring, carb kit, etc. The compression is 145 in both cylinders. My problem is when I run it I have to have the primer knob partly out - showing some red. If I push the primer all the way in once it is warmed up, the motor loses power and RPM`s. It appears to me to be running to rich. The boat shop said they had adjusted the carburetor and idle. I`m several hours away from the shop and didn`t want to drag it back there. I`m not a mechanic but if someone can help me try to make some adjustment, that would be great. Otherwise I will haul it back to the service shop.
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I just went thru the EXACT same problem with my 20hp.Had to keep primer out as you did and had same results.Prior to my issue one of the lead plugs broke off and was loose above my idle screw and was causing it to run lean and after repairing that I still had a problem.I did do a very good cleaning of carb.Did you take welsh plugs out?There could be something in there.Most people don't bother with them...But I also rebuilt fuel pump for good measure and checked for Vacuum leaks in all my hoses and had one on primer hose to manifold.I also had one at the fuel pump gasket to block which I think made it run lean, but not the cause of this issue.I think main culprit was the slow speed/idle circuit.Take your carb off and take idle screw out and flush it out and blow it out.Thats what I did and had instant results.Have to give it another test to double check. and hope what may have clogged it is not still in one of the welsh plugs..
 
oldangler said:
I still think I sense a bit of a hesitation when you throttle up so I'm wondering if I should replace the fuel pump? Any suggestions
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Hesitation when throttle is applied, on that model, would normally be caused by either the throttle butterfly opening too soon in relation to the timing.... butterfly should just start to open when the scribe mark of the cam is dead center with the throttle cam roller..... OR.... a somewhat clogged high speed jet that's located in the bottom center portion of the float chamber, way in back of the drain screw.

A fuel pump plays no part in a problem such as that.
 
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