1972 Johnson 25 Jerks

I'm a noobie in the outboard world and have a couple questions about my Johnson 25 horse. The motor fires up by the second pull and idles great. I'm pull starting because when I try the electric start the solenoid clicks but the starter doesn't kick on. Ocassionally the starter will come up and start to turn but will immediately stop and never actually turns the flywheel. Is this the starter that's the problem?

The other bigger issue is when I have it in gear regardless of the speed about every ten seconds the motor jerks. It does not pop. The best I can describe the sound in text is rrrrrrrrrrbumprrrrrrrrrrrbumprrrrrrrr. Something like that Any advice or wisdom would be greatly appreciated. Thank you?

Re: 1972 Johnson 25 Jerks

Model #25R72 R

Re: 1972 Johnson 25 Jerks

Anybody know what might be up with this thing?

Re: 1972 Johnson 25 Jerks

Problem #1, check the voltage coming out of the solenoid when you try to start it, should be battery voltage, if not replace the solenoid. Make sure all the electrical connections are clean and thight, especially the battery cables.
Problem #2, sounds like the shift dog is jumping in and out of gear under load, any metal particles in the lower unit oil? Could be a spun prop hub, but a spun hub doesn't usually jump in and out like that.

Re: 1972 Johnson 25 Jerks

Check the charge on your battery. If that checks, pull all the wiring connections, clean both post and wire ends and reassemble. Corroded connections are one of the most common problems with weak staring. It is possible, however, that your starter needs to be rebuilt. You can check with a local starter/alternator shop to see if they can do it, or you can buy a new one. Believe it or not, those old starter types are still readily avaialable, because they are still used on small engines other than outboards.

As for the "Jerking," does it do it mostly at or near idle speed? If so, does it sound like a sneeze. If so, your mixture is too lean. If the sound is more mechanical and it does it only with a load on the prop, you may have a worn clutch dog.

Re: 1972 Johnson 25 Jerks

I drained the lower unit oil and was disappointed not only to see milky oil but I could also see metal particles in it too. Looks like it needs a seal and clutch dog. Doh! Is the o-ring on the gear case head typically the culprit for the water leak into the gearcase? Thanks for the help guys.

Re: 1972 Johnson 25 Jerks

Columbia Fishin' said:

I drained the lower unit oil and was disappointed not only to see milky oil but I could also see metal particles in it too. Looks like it needs a seal and clutch dog. Doh! Is the o-ring on the gear case head typically the culprit for the water leak into the gearcase? Thanks for the help guys.

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That leak could come from various places. I have a '73 25HP Johnson and when I had water in the LU oil I found that the driveshaft seal under the water pump had given up the ghost, so if you are checking the impeller at some point, maybe replace that too.