1974 4hp Stuck?

[road kill]

I've had a vintage 1974 4hp Johnson in the garage for over 30 years, its not been used in 20 years and probably don't have 5 hours of use on it since new. Once every few months I take it down, pull the plugs, give it shot of oil and crank it over a few times.
I had it down about a week ago, lubed everything up, and hung it up. Today I decided to get it out, give it a new impeller and fire it up.
Its stuck solid, won't budge. There's oil in cylinders and surely some still in the crankcase, yet it won't budge, not even a fraction of an inch. The prop don't rock at all, the flywheel is as if it's welded.
I can't imagine how something can go from being just fine 5 days ago and now be locked up tight?
I would think that if the pistons were stuck I could rock it a bit at the flywheel?
I tried putting a wrench on the flywheel nut but nothing moves, I can loosen the flywheel nut and the flywheel don't budge.

What is the most likely place for this thing to have seized up? It's got clean fresh oil in the lower unit, I even drained and rechecked it today. Both pistons are about mid bore in the cylinders, I see no rust or anything through the plug holes. If it had sat for 30 years untouched I'd understand, but I just cranked it over and re-oiled it last week and it had good compression and felt fine.

 

[Chinewalker]

Re: 1974 4hp Stuck?

Oiling the cylinders is not a bad thing, but it doesn't get oil everywhere. More than likely your upper main bearing is rusted to the crank. Those 4s have a needle bearing at the top main. If your garage is damp, it may have collected some moisture over the years and rusted up, only just recently it got worse.

 

[Haffiman]

Re: 1974 4hp Stuck?

If totally stuck and not giving a mm, check if flywheel has frozen to the magnets. However engines stored in 'cold' storage may get condensation and water in the lower part of the crank case if hanging on the bracket.

 

[road kill]

Re: 1974 4hp Stuck?

My garage is heated and air conditioned, no moisture at all. Plus I have a dehumidifier running in the basement below.
The motor looks like new, both inside and out. The part that gets me is that it was fine 5 days before I found it frozen.
I even went so far as to put a strap wrench around the flywheel with a 4' bar and it don't budge, not even a fraction of an inch. I poured some Kroil down the carb and in the plug holes last night but no luck so far. The prop also is locked solid, that shaft won't budge either. I've seen seized motors but never one that's as stuck solid as this and never one that seized just sitting, especially as well lubed as this was.

I pulled the flywheel, everything looks clean and shiny around the magnets, no rust at all.
If it were stuck at the lower unit bushing, I'd expect at least some movement in the splines or even driveshaft flex.
If it were only one crank bearing locking the motor I'd expect that 4' of leverage would break the free or at least move it a little. I borrowed one of those stick cameras to look in the plug holes, and it's shiny clean in there, no signs of rust at all.

I've always had oil dripping from this motor, oil put in the cylinders eventually makes its way out the exhaust over time, I've always just kept a bucket hanging from the lower unit to catch any drippings. My thoughts were that if I kept it well oiled it would preserve it.
Of all the motors I have dealt with this is the last one that I would ever expect to seize up.
If it were the slightest bit tight or if it felt even a bit different last week I'd have noticed it. It was 100% fine, I pulled the rope, plugs out, cranked out any old oil, moved the pistons to mid bore and filled the cylinders with clean oil and shot some down the carb as well. I've done this several times a year since I bought it. I do it to any of my motors when they sit.
What's even more odd is that I've trash picked these motors that looked like they've been run in salt water and never once found a seized one.

 

[Haffiman]

Re: 1974 4hp Stuck?

Looks like you are in for a tear down project.

 

[boobie]

Re: 1974 4hp Stuck?

Drop the G/C to find out where the prob is. G/C or power head.

 

[Rick.]

Re: 1974 4hp Stuck?

Agree. Separate and conquer! I am at a loss as to what to say except get rid of the four foot snipe, it will only make things worse. I'm surprised your transom bracket and/or internals hasn't blown apart. That is a disgusting amount of torque to put to that nice little engine. Best of luck and do keep us posted. Rick.

 

[bigboi]

Re: 1974 4hp Stuck?

your rod bearings are locked up it simple you told yourself the problem you only lube the cylinders you have to lube the whole thing rod bearrings and all or it will lock up which it has i would tear down get it unlocked and when you crank it every now and again i would run a little extra oil to keep everything extra lubed

 

[1946Zephyr]

Re: 1974 4hp Stuck?

Holy crap, I never heard anything like this either. I would think that if you turn a motor over, it should still be free the next week.

 

[road kill]

Re: 1974 4hp Stuck?

The motor was fogged with spray lube, usually wd40 or CRC regularly through the carb with the throttle plates open, along with oil in the cylinders. I can't imagine it not getting enough lube in there as often as I've kept after it. Its not like it's been sitting in some old barn exposed to the elements either. It may as well been kept in the house since the garage is carpeted and semi finished, the garage is basically a pool room and bar with my toys stored on display. This motor, the canoe it was bought for, and two motorcycles also reside there. The one bike hasn't been used since 1979 and it never seized up, nor has any of my other antique motors.

I guess it's a weekend project now, I'll pull the lower and see what's up. If the rods are stuck, will I be able to get to them to release the rods and get it apart with both pistons mid bore? Its sure going to hurt to tear into a spot clean little motor like this. The only sign that it's not brand new is the trail of oil from the exhaust holes over the years.

 

[Smokey496]

I may have missed something. Did you remove the plugs and drain the oil out of the cylinders? Just asking.

 

[JDusza]

Re: 1974 4hp Stuck?

If you're a daring soul, you may be able to free the "stick" by tapping a wooden dowel on the pistons. Pull the plugs and get a wooden dowel that will fit inside the pug hole; about 3/8". Tap gently on the dowel; best if you have another set of hands trying to turn the flywheel at the same time. I wouldn't tear it down unless you absolutely have to. You have significant risk of breaking studs off in the block and those will require serious shop set-up to clear out and retap. Be sure to use a wooden drift and not a metal one. Metal will definitely damage the top of the piston. After it frees up, flush everything good with a penetrating oil.
Good luck!

 

[Haffiman]

Re: 1974 4hp Stuck?

If a long shaft version, it might be the bushing in the extension that has frozen.

 

[Chinewalker]

Re: 1974 4hp Stuck?

I would NOT torque too much on that flywheel. I had a '76 Johnson 4hp come into my shop that someone had tried to unfreeze with a breaker bar. Ended up snapping the caps off both con rods. Those motors have aluminum rods and they WILL bend and CAN break if you are really yanking on them. Best thing to do is tear into it. VERY simple motors to tear down. If the motor is as nice and clean as you say, then it is worth the efffort...