1974 Johnson 25 hp

[jrichson]

Hello all,newbie here. I have a 1974 Johnson 25 hp that has a miss at idle. I took carb apart and cleaned and kitted it. No difference. Checked points and found oil all over breaker plate.Points were very used and burnt, so I replaced them. No difference.Compression is 145 psi up and down. Any ideas?

 

[Chinewalker]

Re: 1974 Johnson 25 hp

Hi MMFan,<br /> The oil all over the points suggests that the upper main seal is probably leaking. Not only is oil leaking out, but more than likely you've got air leaking in, which can create a lean condition at idle, which is probably the cause of your miss. You'll need to replace that seal - I can't remember if you can get it out without splitting the crankcase or not. Worth a look... <br /><br />- Scott

 

[itstippy]

Re: 1974 Johnson 25 hp

You need a special tool to replace the top seal without splitting the case. The tool screws in and pulls the old seal out all nicey-nice without ruining the collars. IMO It's worth it to remove the flywheel and armature assembly yourself and then take the motor to a well equiped OMC shop and have them replace the seal.