'76 Johnson 15hp is haunting me please help!

[Johnson76]

I have a 1976 15 hp Johnson that will run for about a minute and die, then I can restart it and it will do the same thing.
I tried pumping the primer bulb when it starts to die but that doesn't help and neither does choking it and I've noticed the plugs are wet after this.
The things I have done to the motor so far and hasn't changed a thing is this:
Rebuilt the fuel pump and carburator
Replaced the thermostat, one coil, points and condensors
Spark plugs I've tried champion UL81J's and B7HS's
Fuel mixture is 50:1
The tank is clean and the gas/oil mix is new, the primer bulb and fuel lines are also new.
The compression is 100 for each cyliinder.

Please help, i'm going broke trying to get it fixed.

Thanks, Johnson 76

 

[DJ]

Re: '76 Johnson 15hp is haunting me please help!

Most likely your carb. float is sinking, thus the RICH mixture.

 

[bktheking]

Re: '76 Johnson 15hp is haunting me please help!

Have you tried disconnecting the 2 kill wires from the stop switch?

 

[Johnson76]

Re: '76 Johnson 15hp is haunting me please help!

When I rebuilt the carb I checked to make sure the float would float and it didn't leak by submersing it in gas, i didn't see any bubbles and it did float, can it still be bad?

The kill switch I pulled it apart and the small cone shaped button fell out so I got it to fit back into the rubber button like it suppose to, then took a bit of super glue and put on it so the cone couldn't fall out again, then i checked the button with a meter to make sure it was only ground when pushed.

 

[bktheking]

Re: '76 Johnson 15hp is haunting me please help!

Disconnect the 2 kill wires and try it, I wouldn't trust a re glued stop switch.
As for the float, was it the cork style or new composite float? Was the float parallel to the carb body when the carb was flipped upside down? Did you remember to attach the needle to the float with the clip???? That's a common one.

 

[Johnson76]

Re: '76 Johnson 15hp is haunting me please help!

I unplugged the wires to the kill switch and started it again, it ran again for about a minute and died.

The carb float looked like a composite but could have been cork, not positive on that one.
I set the float paralled with the carb when flipped upside down, it was set a little lower (meaning the needle would shut the gas off at a lower level when flipped right side up) when i took it apart.
I did the same thing before i replaced and changed everything so I'm not gaining on it at all.

 

[Johnson76]

Re: '76 Johnson 15hp is haunting me please help!

Oh i forgot yes i did hook the needle valve on to the float with the spring clip when i put it together.

 

[AlTn]

Re: '76 Johnson 15hp is haunting me please help!

you might try rigging up a gravity fed fuel supply to your carb...think iv bottle....that should fill the carb bowl.Temporarily fit a piece of plastic tubing to the outlet nipple on the fuel pump and direct that flow into some container.If the motor runs, you can see if the fuel pump is pumping properly. If the motor doesn't run any longer than it has been...you'll at least know that your fp isn't your problem. What you're describing sounds like either the carb isn't refiling the bowl..and it runs dry, or the fuel pump isn't working properly.

 

[bktheking]

Re: '76 Johnson 15hp is haunting me please help!

Ok, starting to think perhaps you are losing spark instead of fuel. Have you confirmed spark on both cylinders? When you had the flywheel off, did the mag plate have any movement whatsoever?

 

[Johnson76]

Re: '76 Johnson 15hp is haunting me please help!

I will get a new float and put in the carb, and try it again, the plugs are wet when it dies so too much fuel or not enough spark.

Should this motor run fine on muffs or does it need to be in a tank?

 

[johnsonoutboards]

Re: '76 Johnson 15hp is haunting me please help!

"I have a 1976 15 hp Johnson that will run for about a minute and die, then I can restart it and it will do the same thing."

-that sytom almost sounds like a sytom of thermal break in the electrical system it gets warm and stops working let it cool for a min it will start back up

"I tried pumping the primer bulb when it starts to die but that doesn't help and neither does choking it and I've noticed the plugs are wet after this."

-if you motor is a twin cylender go out and buy 2 in line spark testers you can normaly buy them for $3.00-$10.00 each plug them on and watch them it watch what the lights do when it starts to die see if they ireguler if so you have and electrical problem

"The things I have done to the motor so far and hasn't changed a thing is this:
Rebuilt the fuel pump and carburator
Replaced the thermostat, one coil, points and condensors
Spark plugs I've tried champion UL81J's and B7HS's
Fuel mixture is 50:1
The tank is clean and the gas/oil mix is new, the primer bulb and fuel lines are also new."

- thats a good start have you tryed the new E3 spark plugs i find they work good in finiky motors

-how did the wireing look when you changed the points and condencers were the wire stiff and brittel at all did you check the wires for any small cracks may be a pinched wire if the wires are getting old looking i would change them
"The compression is 100 for each cyliinder."

-for me a 100psi is getting kinda on the low side for my liking on a 2 stroke i usly like to see 120psi or higher for me when a 2 stroke get to around 100psi and lower its kinda gets in to the area were it should be rebuilt

"Please help, i'm going broke trying to get it fixed."

-i know this feeling all to well

i hope this help sorry about my bad spelling its never been one of my strong points