only running on one cylinder

[harlang]

I have a 1962 18 hp johnson. It starts ok and runs rough. When I get it to full throttle it run on one cylinder at first then the second one starts to hit for a second here and there, then it will fire on both cyliners and run great until I slow it down again then it only hits on 1 cylinder again and does the same thing again when I go full throttle again.

 

[F_R]

Re: only running on one cylinder

I have a 1962 18 hp johnson. It starts ok and runs rough. When I get it to full throttle it run on one cylinder at first then the second one starts to hit for a second here and there, then it will fire on both cyliners and run great until I slow it down again then it only hits on 1 cylinder again and does the same thing again when I go full throttle again.

Time to check for cracked coils. If it isn't that, a bad spark plug wire, arcing through where it is clamped under the armature plate.

Of course, it could also be something simple like dirty points or a bad spark plug.

 

[harlang]

Re: only running on one cylinder

Coils look good and both plugs have good spark. It only has a single carb but could something in the carb still cause only one cylindar to foul? Also the motor has champion plugs J6C instead of the recommended J4C.

 

[F_R]

Re: only running on one cylinder

Coils look good and both plugs have good spark. It only has a single carb but could something in the carb still cause only one cylindar to foul? Also the motor has champion plugs J6C instead of the recommended J4C.

"Tain't the carburetor. As you suggested, a single carb feeding both cylinders can't just feed one. The J6C plugs in itelf won't cause it, but one of those could be bad. Have you tried new ones? Can't hurt to try and that might be the only thing wrong with it. Could also be getting water in one cylinder.

But you haven't convinced me yet that it isn't the ignition system. If not plugs or water, I have to go back there. How good is your "good" spark? Will it jump a 1/4" gap? Are the points clean and in good conditon? Remember, they have to make and break good contact up to around 75 times per second! And how about those spark plug wires? Are you sure they aren't arcing out at certain angles of bend? Have you run a continuity check on them and the coils' secondary windings? Just looking good doesn't get it.

The only oher thing that might cause running on one cylinder is the fuel pump. If the diaphragm is perforated, it will flood one cylinder. But your description doesn't fit that.

 

[harlang]

Re: only running on one cylinder

Thanks, I don't have a ton of experience with motors or many of the right tools to deal with them but I am pretty good at figuring things out and dont have the money to take it in. So thanks again I will try a couple things and maybe get a new head gasket to see if it is water getting in.

 

[tashasdaddy]

Re: only running on one cylinder

try it in the dark, see if the plug wires are arching to the block. i am in total agreement with F_R. good info here http://forums.iboats.com/showthread.php?t=299680

 

[harlang]

Re: only running on one cylinder

Finally rented a puller,didn't realize I could get one for free at checker or I would have done it a while ago. Took off the points and coils and cleaned everything up and now it runs like a champ. I will probably still replace everything when I get the money but thanks everyone for your help.