1988 Johnson 8 hp Help! Seized?

[Harry B.]

I've got a 1988 8hp that I just bought from my uncle for $150.
The throttle can go from idle to full throttle in gear, reverse or neutral. It seems, I would think, that this may be my problem, safety limitations that I cant seem to find or correct that limits it from starting in gear and/or at full throttle.
The starter engages the flywheel but the flywheel doesn't move.
In neutral the prop spins freely. In gear however, it wont turn.....(maybe it is seized up from sitting without lube and heating and cooling and some humidity rusting the piston to the cylinder wall).

Any ideas? Any bets on what it is? Thanks in advance for some direction.

 

[racerone]

Will the flywheel move back and forth slightly or is it absolutely locked solid ?

 

[Chinewalker]

As Racerone noted, try the flywheel by hand. That motor should have a lock-out on it for the recoil to prevent it from being pulled at too high a throttle setting.

If it is stuck, I prefer a complete disassembly as it is often the case that stuck pistons mean rusted bearings on the crankshaft. Do not torque away on the flywheel as that motor has aluminum rods and they can bend/break if you put enough effort into trying to turn the flywheel. Even if you were to unstick the powerhead, its life expectancy might be measured in minutes or years - you just won't know. If you get it apart and the crank bearings are clean, you are also better able to clean up the rusted bores and rings and reassemble from there.

Also a good idea to pull the gear case off (three bolts) and check to make sure the issue is not inside the lower unit.

 

[Harry B.]

The flywheel turns back and forth quite a ways. Probably 1/3 or so of a turn.
There is nothing preventing it from being started in gear then? I can see the limiter on the recoil starter but that's not what's keeping the flywheel from spinning. It's something else. Thanks for the recommendations as well. I'll tear into the lower end and see what I find.

How technical is it to tear down the power head to the piston's and cylinder head. I'm just a fair backyard mechanic at best.
What do you think about: http://www.seized-engine.com/boat-motors.html

 

[Chinewalker]

If it turns that much, it could be one of a few things.
Lower unit is a possibility as a broken gear tooth could be binding it. I'd start here, as you have to replace the water pump anyway, right? (Assuming it's not a catastrophic issue keeping the motor from turning.)
Or, it's possible your motor has the wrong spark plugs in it. If someone has installed long reach plugs, they may be hitting the piston head. You should be running Champion L77JC4 plugs.
Could also be something in the magneto has let loose. I've seen the small Phillips head screws that hold the mag to the base plate back out and get caught between the flywheel and one of the items bolted to the mag plate.
Also possible something in the carb or intake plate has come loose and is floating around inside the crankcase. Least likely of these, but certainly possible.

 

[Harry B.]

I should probably clarify. The flywheel turns freely...... zero resistance, (probably more like a quarter turn) but hits hard after that and won't budge, even the slightest bit, either clockwise or counterclockwise.
The prop, while in gear wont turn at all.

The spark plugs are air gaps, I believe Champion V78's, so it's not that.

 

[racerone]

3 bolts remove the lower unit and that will tell the story.------It is either the lower unit or the powerhead.

 

[Harry B.]

Thanks for the help and direction! This forum is probably filled with some of the most helpful people on the planet and also the best place to find some real knowledgeable people who know boats and boat motors.
I'm going to tear into it tonight and I'll report back what I find out.

 

[Harry B.]

All's well with the lower unit, which means she's seized up I guess.
I don't know whether I have the time or knowledge to be tearing things down to get to the rings, pistons and bearings unless it would definitely be worth it to do so......and then, if I do, I might not be able to get through it. I've heard a lot of headache and heartache busting bolts etc.

What's folks thoughts about: http://www.seized-engine.com/boat-motors.html

Or should I try transmission fluid, penetrating oil or something else or..............Should I tear it down and see if I'm a better mechanic than I think I am?

 

[ryanorillia]

since it's your uncle i'd try to get my $$ back..just my .02

 

[Harry B.]

I'm pretty sure I can part it out for more than $150. I'd really rather have the running motor though.

 

[Chinewalker]

Try pulling the flywheel to make sure there's nothing caught in the magnets.

 

[pro-crastinator]

Based on what I have read here, the motor just does not sound like it is siezed.
A little work is in order to get more data.

 

[Xcusme]

Ha! My choice is with Chinewalker's suggestion with the magnets. It would be best to remove the flywheel and have a look around before you think about parting out the motor.

 

[Harry B.]

Well, I removed the flywheel and indeed I found metal that wasn't supposed to be floating around under there. Unfortunately it just got under there when I pulled it off.
The key broke off flush against the shaft.

It's still froze up as well.

This is getting fun now.

 

[racerone]

Pull the cylinder head off and see if both pistons move properly.

 

[Chinewalker]

Might find only one piston actually moving....

 

[racerone]

Perhaps the motor came to a " dynamic halt " and that sheared the flywheel key.

 

[Harry B.]

I think I'll give it a whirl. I don't have a lot to loose at this point.
My uncle doesn't remember any problems with the motor, but he, at anyone time (unless it's before 11 or so in the morning), usually has a dozen plus beers in him so I'm not sure what he truly remembers and what he doesn't.
I really didn't want to tear into the motor too much, but I've got some time on my hands to mess around with it. I've worked on outboards a little bit for the past 10 years or so, but never with the internals. This will give me some knowledge about some things either way.
I appreciate the help and support, and I'll share updates as I go along. Thanks guys.

 

[Harry B.]

Yup, major catastrophic failure.
The connecting rod give way from the crankshaft. Lots of aluminum shavings everywhere.
Looks like a parts motor unless you guys have another option for me.
With that kind of a failure and pieces of aluminum in the cylinder is it toast?