1976 johnson 9.9 intermittant loss of RPM

[dan29to30]

I have an older seahorse that has been giving me some trouble. It used to misfire intermittantly pretty bad which I took care of with new coils, plugs, clean and adjust points to 0.020 . the problem I have now(it did happen also previous to repairs) is an intermittant lack of engine rpm while the throttle is full out. It will run fine at full out and would probably stay there for a long time, but if I go down to idle to clear weeds or something, it will not go back up to full throttle. after puttering around for sometimes 5, 10, 20 minutes or whatever, it will slowly catch itself and resume normal high speed. I have rebuilt the fuel pump and the carb. checked the adjustment of the timing between baseplate and roller for throttle on carb. primer bulb replaced and getting plenty of fuel. PLEASE HELP!!!

 

[Rick.]

Re: 1976 johnson 9.9 intermittant loss of RPM

dan29to30: What can I say, it seems you've done everything a right thinking repairman would/could do? There are a couple of things that come to mind so I'll give it a try. Next time it is acting silly, pull your plug wires one at a time. I know you replaced the coils but it could be that one of the new ones is acting up. The other thing would be your spark going to ground. Again, when it's acting up try to see if you have spark going to ground somewhere along the wires and boots. It would be an easy task in the dark but more important to try to see it when your motor is giving you trouble. Best of luck and let us know if you find the problem. Rick.

 

[dan29to30]

Re: 1976 johnson 9.9 intermittant loss of RPM

it did have this problem once before I replaced the coils and plugs and did the other work. it would seem too much of a coincidence to have the exact same problem with new parts installed. thanks

 

[jay mendoza]

Re: 1976 johnson 9.9 intermittant loss of RPM

Try pulling the choke and see if it picks up.

 

[Daviet]

Re: 1976 johnson 9.9 intermittant loss of RPM

When you overhauled your carb did you remove the high speed jet and clean it with a fine wire and blow everything out with compressed air? You can use a timing light to check spark when problen occours. As suggested before, when problwm occours, pull the choke out. If it picks up and runs ok, you have a fuel supply problem. You might try pumping the primer bulb also, bypasses fuel pump.

 

[dan29to30]

Re: 1976 johnson 9.9 intermittant loss of RPM

I put my hand over the carb which is equivalent to pulling the choke and had no change. I could not remove the hi speed jet but shone a light in and could see the passage was clear. I also removed the welsh plugs to check passages better for debris. the carb was extremely clean inside with no varnishing

 

[Rick.]

Re: 1976 johnson 9.9 intermittant loss of RPM

it did have this problem once before I replaced the coils and plugs and did the other work. it would seem too much of a coincidence to have the exact same problem with new parts installed. thanks

Don't be so sure. I've put brand new defective parts on my vehicles before. Go back to my previous thread about checking for spark, or don't. Your right your high speed jet is not removable ( I tried that and cost me a new carb.) Rick.