56 johnson 15 hp not running well under load

[rossmartin]

I have rebuilt most all of this motor, I put in new points, a makuma pulse vacume fuel pump, new plug wires, new plugs, condensers had been previously replaced and had no cracks so i left them, rebuilt carb, and put in a new water pump. The motor now starts and runs but not well, in nutral it seems to run well but once I put it in gear it will not wind up and go. it runs best with high speed needle valve open about 1/8 turn.I think it is flooding but I put in a new carb float and needle so I do not know why it would be. It will only push the boat a little faster than it should at idle.

 

[F_R]

Re: 56 johnson 15 hp not running well under load

Sounds like it is running on once cylinder. Did you check the compression? If that is ok, revisit the ignition system.

That is, assuming your fuel pump installation is ok.

 

[samo_ott]

Re: 56 johnson 15 hp not running well under load

You don't mention new coils? it definitely sounds like its running on 1 cylinder. Pull the plug wires off 1 by 1 and see if the engine speed drops the same or if 1 makes no diff.

 

[rossmartin]

Re: 56 johnson 15 hp not running well under load

I did not change the coils, but they are not original, so i assumed that they were probally good. I started it and the bottom cylinder is not any good, So I am going to pull flywheel and switch the coils and see it the bottom cylinder comes alive and the top one dies. If this is the case then I know i have a faulty coil, can I just change one or is it best to change both.

 

[asdasc]

Re: 56 johnson 15 hp not running well under load

Just curious, how do you guys go about pulling a plug wire on a running motor? Don't you get the shock of a lifetime when you grab a plug wire on a running motor?

Also, just because it is a pain to get under the flywheel, whenever I have to get in there, I replace both coils, condensors, and points - just so that I don't have to pull it all apart again for 20 years.

 

[rossmartin]

Re: 56 johnson 15 hp not running well under load

It is def. a bad coil, I switched them and the live cylinder moved, Now do I have to change them both or can i just change the bad one.

 

[asdasc]

Re: 56 johnson 15 hp not running well under load

that is a question only you can answer. The other coil will cost about 25 bucks. What is it worth to you to never have to pull apart the flywheel again, or to get stranded on the water and have to row home?

You can guess what I would
do!

 

[samo_ott]

Re: 56 johnson 15 hp not running well under load

Just curious, how do you guys go about pulling a plug wire on a running motor? Don't you get the shock of a lifetime when you grab a plug wire on a running motor?

Use a rag. Or, I bought a spark plug wire puller at my local auto store for a few bucks and it sure makes it a lot nicer than it used to be... I'm getting old!

 

[samo_ott]

Re: 56 johnson 15 hp not running well under load

It is def. a bad coil, I switched them and the live cylinder moved, Now do I have to change them both or can i just change the bad one.

That's a lot of work to swap coils. I wouldn't have bothered! I'd just have replaced em. Thus I believe you should change em both. Why mess around and have to go back in there. And then you have a spare good coil for your next engine