old johnson lack of power

[rustycat2007]

hi i have a 1971 johson 40 hp outboard and it will start and idle but boggs down when you put in gear and throttle up. It has some power in reverse but very little in forward any ideas?

 

[Daviet]

Re: old johnson lack of power

You need to start with some basic checks, compression, spark and fuel delivery. ompression should be even between cylinders and above 60 to 70 psi. Spark should jump a 1/4" gap and be bright blue and have a snap to it. The fuel system should have fresh gas/oil mixture and the fuel pump should pump solid pulses of fuel. If the engine has been sitting or was not winterized properly, it might be time for a carb overhaul. Has anyone been messing with the carb adjustment?

 

[rustycat2007]

Re: old johnson lack of power

i did some tinkering this morning and found out more. i started the motor and let it idle. then i pulled the top cyl's sparkplug wire and this killed the motor. i did the same with the bottom cyl and it did not affect the way it was running so the motor was only running on the top cyl. so i pulled the flywheel and found that the points that correspond to the bottom cyl dont connect when the cam is turned so i ordered new points and this should cure my problem right?

 

[Daviet]

Re: old johnson lack of power

Sounds like you are on the wright track. If the points are not makeing contact you might be able to readjust them to make sure that is your problem.

 

[rustycat2007]

Re: old johnson lack of power

well i bought the motor for 100 bucks and i think these are original points so since i already have it apart ill go ahead and replace them because they dont cost much and theyll last a little longer. but ill try adjusting them and see if that does it. thank you for your help.

 

[jeff_smith_0423]

Re: old johnson lack of power

Replace the coils while you're in there - if they're green, they need to go.

I've got a 9.5 in my garage right now that ran happily on a one cylinder as long as you opened it up just a tad. I had no idea until i pulled the plug wires.

 

[electricakash]

Re: old johnson lack of power

I have a 68 Johnson 9.5 that has the same problem, I recently replaced the coils, points, plugs etc. The motor started and ran fine on one cylnder, but after changing all of the above she wont even turn over now?? I don't know what to think, very frustrated, about to start on fuel delivery problems????? any suggestions would be awsome!!

 

[Daviet]

Re: old johnson lack of power

electricakash, you need to start your own post so that you will not get lost.

Do you have good spark on both cyliners, will it jump 1/4" gap and bright blue? If so try squirting some oil/gas mixture in carb and see if it will start. Will tell if you have a fuel problem.