4 hp johnson 1974

[b1bofz13]

motor runs fine in tank but when installed on boat after 5 minutes running at
cruising speed falls on one cylinder and then stops

 

[TN-25]

Re: 4 hp johnson 1974

It sounds like you may not have your gas tank vent open. Make sure the fuel tank vent is working. If I remember right that motor uses a little half-height tank (3 U.S. or 2? Imperial gallon) and they had a separate vent. On other single line metal tanks (& newer 1/2 height tanks) you simply ran the gas cap twisted a quarter turn open to vent.

 

[Rick.]

Re: 4 hp johnson 1974

Have your coils ever been changed? If your loosing spark after she warms up that would be my first investigation. Pull the flywheel and have a look at them. If they are cracked get new ones. With the flywheel off have a good look at your points and re-gap/replace them as you see fit. When I first got my 71- 4HP Evinrude it would die for no reason after running anywhere from five to thirty minutes. I put a carb. kit in it and that fixed the problem. However if your loosing spark to one cylinder I do suspect your coil. Best of luck. Let us know what you find. Rick.