1981 Johnson 90 HP Resurrection

[9711waving]

I?m trying to bring a 1981 90 HP motor back to life for my grandson. It hasn?t been used for 10 years. We removed the plugs and oiled the cylinders with Marvel Mystery Oil and let it sit for a few days. Then we manually turned the flywheel to see if they were loose. No problem turning it. We then hooked up the battery and tried it with the plugs still out. It spun like a top. We then put the plugs in and tried it. It would only make ? turn and then stop.

Any ideas about what our problem is? Hopefully not problems are.

Thanks

Rockport Del

 

[metriccrescentwrench]

Re: 1981 Johnson 90 HP Resurrection

There are some threads on here about bringing back an engine that's been sitting. Sorry I can't point you right to them, but if you use the search feature I'll bet they'll turn up.

I've also got an '81 Johnson 90, previous owner had neglected it but now it's been running great with zero issues for over 2 years. One thing I found was that the specified plugs would tend to foul somewhat quickly so went one heat range hotter and it's much better (I use my boat for everything from cruising to fishing to pulling skiers and wakeboarders) - I don't recall the part number for those plugs off the top of my head but will look it up tonight.

Have you done a compression check? Tested spark with a tester? What spark plugs did you put in (hopefully they're not too long and hitting a piston)? Are you using a new, fully charged battery? It's also possible there's a poor connection somewhere so that the starter isn't getting full voltage and is stalling out when the engine hits a compression stroke. A failing solenoid or starter could cause the same type of problem, a digital multimeter is going to be your best friend for finding these types of electrical problems.

 

[9711waving]

Re: 1981 Johnson 90 HP Resurrection

Tried all thos things.

Thanks for the interest.

Rockport Del

 

[emdsapmgr]

Re: 1981 Johnson 90 HP Resurrection

With the plugs in, try jumping the starter direct to the battery and see if it will spin the engine normally. If it will not turn over, maybe a bad starter-maybe it just needs brushes. If it turns over ok with the jumper cables, you may have a bad starter solenoid.