1969 Johnson Seahorse 25 HP not firing on one cylinder.

Rocjohns

Cadet
Joined
Apr 13, 2014
Messages
15
Hello all, need some assistance double checking my steps to get my motor running.

I have a 1969 Johnson 25 HP that wasn't running when I got it. Needed a fuel pump which I bought and when installed, it pumped nicely.

It ran after after I installed the fuel pump for a few minutes then it died. I can get it to fire, but for only a few seconds. Not it has trouble firing at all.

I pulled the carb off (which has had a rebuild kit put on it recently), but it looks like it wasn't winterized properly and a bit of green corrosion on float needle. I cleaned it all up and got needle unstuck so it should be getting gas now. Probably was stuck and the reason why it wouldn't fire after a while.

The guy I bought it from said he put new coils on it, but after doing the stupid human trick of holding spark plug while my wife cranked it (she always enjoy's this), only one plug is firing. So now I have pulling the flywheel (doing it without pullers based off a few post I saw but yet to successfully try), I am going to check the coils.

My question is... is there anything else I should check? I am not 100% sure how to check points and how this plays into my issue if it even does.

Any suggestions will be helpful. I have great compression and the engine looks good (maintained well over the years till the last guy got it).

Thanks,
Bobby
 

kevinwd1

Petty Officer 2nd Class
Joined
Jul 8, 2013
Messages
130
Re: 1969 Johnson Seahorse 25 HP not firing on one cylinder.

I had the same problem with a 4hp motor. Turned out to be dirty points. I fixed it by removing the points and rubbing them against some fine sand paper. Reinstalled them with the correct gap and problem solved.
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 1969 Johnson Seahorse 25 HP not firing on one cylinder.

Does your local auto parts store rent tools?
You can use a harmonic balancer puller with grade 8 bolts to pull the flywheel.
Go ahead an purchase an adjustable gap spark checker, not very expensive, and set it to 1/4" and recheck the spark on each cylinder.
You should get a bright blue spark with a snapping sound to it.
When you get the flywheel off check the coils for cracks and the condition of the points and see if they are properly adjusted.
Make sure to torque the flywheel to the proper spec when you install it.
 
Last edited:

AlTn

Commander
Joined
Mar 9, 2010
Messages
2,813
Re: 1969 Johnson Seahorse 25 HP not firing on one cylinder.

look under the Top Secret Files at the beginning of the forum posts...scroll to Universal Magneto Troubleshooting...most of your ?'s should be answered
 

Rocjohns

Cadet
Joined
Apr 13, 2014
Messages
15
Re: 1969 Johnson Seahorse 25 HP not firing on one cylinder.

Excellent stuff. Will check out top secret files...
 

Rocjohns

Cadet
Joined
Apr 13, 2014
Messages
15
Re: 1969 Johnson Seahorse 25 HP not firing on one cylinder.

So here is my verdict and things I did to get there.

Took the flywheel off with harmonic balancer. Worked like charm.

Took coils off and did continuity test on red/black wire and succeeded for both.

Checked plug wire continuity. Looked good.

Put flywheel back on with out nut and manual starter. Just wanted to see if I was getting spark. Same as before. One plug fires hard, but other doesn't; however, I felt the faintest of a pulse.

Here is my question, it seems to be points or condensers. I had a hard time understanding how to test those. I tried to gently sand the bad on, but still no spark. Is there a quick easy way to test them? Do you all feel points are probably the problem?

Thanks again...
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 1969 Johnson Seahorse 25 HP not firing on one cylinder.

You can use an ohm meter to check the points for proper operation. You can do a search here or I am sure you-tube will have a vido on how to do it.
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: 1969 Johnson Seahorse 25 HP not firing on one cylinder.

Try cdielectronics.com.
 
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