1958 Johnson Seahorse 18 hp Problems

[nathankukson]

I just got done replacing coils, condensers, points, plug wires, and the plugs. The carb has a new float and the neetle valves look like they are in good condition. This model has a pressure tank that does not leak air.

I took it out and it started right up and idled only on one cylinder. The other would fire only once in awhile making the engine sputter. When I accelerate it seems to sputter on one cylindar but at some point when I am turning the throttle both cylindars kick in and it runs just great at high speeds. I can get it to idle on 2 cylinders once in awhile but not consistantly. It seems to me the gas and the spark are not in time at the middle speeds. I am thoroughly confused what to try next before I give up and send it into the shop.

 

[jbjennings]

Re: 1958 Johnson Seahorse 18 hp Problems

Nathan,
Welcome to the forum. Here's what I'd look at:
1)Did you screw the new plug wires into the coil points, or just try to shove them in as far as possible?
2) Look at the cam roller at the top of the carb which the armature plate shoves forward when you twist the throttle. When the throttle is turned from the bottom of it's travel, you should notice (with the carb's air silencer off so you can see in the carb throat) that as the roller starts to touch the armature cam, it should touch at a little mark on the cam and the throttle plate in the back of the carb throat should just start to open. This means that the throttle plate is synchronized with the timing. If the throttle plate doesn't just start to open as the cam roller hits the timing mark on the armature cam, it's not sychronized and needs adjustment.
3) At night with it running in a barrel, see if you see any electrical arcing of the plug wires and such.

Good luck,
JBJ

 

[1stgenbird]

Re: 1958 Johnson Seahorse 18 hp Problems

I agree that you need to ensure that the plug wires are screwed into the coil. I replaced the coils and plug wires on my 57 Evinrude 18 last season and pushed the wires in. Got it back together and no spark. I didn't know the wires screwed in until I read some posts on this site as most of the repair manuals that I have read give no direction on replacing the plug wires. The old Evinrude service manual I have shows the wire core being soldered onto the coil. Maybe the plug connection of the coils were different back then and did not have the screw point.

 

[nathankukson]

Re: 1958 Johnson Seahorse 18 hp Problems

Well this morning I took the motor apart and when I popped the flywheel off I found the coil wires had been frayed by the cam. The plastic covering was damaged revealing the bare wire which in turn was my problem. When I repaired the wire I did twist on the wires like you said and I adjusted the metal advance so It would open the throttle as soon as it hit that mark.

I put It all back together and brought it down to the lake and it ran great with some carb adjustments. Thanks with the great reply!

 

[jbjennings]

Re: 1958 Johnson Seahorse 18 hp Problems

Great! I always like to hear the outcome.....
Glad she's running good for you. the '57 and '58 OMC 18's are some of my favorite motors.
Later,
JBJ