1978 Johnson 15 hp

[2Stix]

Just bought this. It's in great shape looks wise and feel lucky to find one this nice. But I have a few concerns about getting this motor back in great mechanical shape. First off, I drained the lower unit oil and it was black. I pulled the plugs and found gunk on them. The motor started and idled great when i bought it so i was surprised to see that. Not sure what to do now to get this thing mint. Thanks

 

[oldcatamount]

Re: 1978 Johnson 15 hp

If it ran good with old plugs it'll run alot better with a new set. Get some fresh gear oil in there and enjoy your motor!

 

[OptsyEagle]

Re: 1978 Johnson 15 hp

By gunk, if you are talking about wet oillyness on the the plugs, that is normal, especially if it was idled in a barrel or on muffs for any length of time. Make sure your spark plugs are Champion QL77JC4 gapped at 0.030" and you are good to go. If you do not know when the water pump impeller was last changed you should do that also. They need to be changed at least every 5 years and they need to be changed when they are still working good, since to wait until they fail is to do it after you just destroyed your motor. A little late if you ask me.

 

[Rick.]

Re: 1978 Johnson 15 hp

Black is good on the gear oil. That's what to expect. Your new motor does look to be in really nice appearance. You probably got a good one. I would check compression right away and write it down so that you have a reference point going forward. Here are a couple of sites that will be of assistance regarding your question of what to do to it. Leeroy has such in-depth knowledge about these motors and shares his knowledge so willingly. It is a must read IMO. Also, I've recently realized his articles are often edited so a revisit from time to time is a good idea. Best of luck. Rick.
http://forums.iboats.com/showthread.php?t=299680
http://www.leeroysramblings.com/

 

[bonzoscott]

Re: 1978 Johnson 15 hp

I have the same motor except a long shaft. Mine required extensive carb work. I think my motor may have been submerged as I found mud in many places and still all the same ignition components. I think it is bullet proof!

 

[2Stix]

Re: 1978 Johnson 15 hp

Thanks for all your tips and advice!! Very appreciated. Matt