120hp Force crankshaft and stator

I have a 1996 120hp Force outboard. The stator went bad with a carmel looking substance oozing from the top and side of the stator. When I wne to take the flywheel off, I took the nut off that holds the flywheel on, I noticed there was a crack running vertically down the crankshaft from the top about 3/4 inches long. The cack stops above the part of the crankshaft that holds the flywheel.

Has anyone encounterd this before? Would anyone know if this will cause a problem and continue to crack farther down the crankshaft? I hate to have to replace the crankshaft or get a rebuilt powerhead because I don't want to put that kind of money into a boat that isn't worth anything. Any thoughts and insight would be appreciated.

Re: 120hp Force crankshaft and stator

Hmmm! Very interesting! Photos please.

Re: 120hp Force crankshaft and stator

Frank Acampora said:

Hmmm! Very interesting! Photos please.

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See attached photo. The center of the crankshaft at the end is hollow down the middle for about 1/2 inch. The crack extends just slightly beyond where the center is hollow. The crack was there and noticable prior to me taking of the nut that holds the flywheel.

Re: 120hp Force crankshaft and stator

WOW!

That is a difficult call: On one hand, the engine was running and the flywheel is on an undisturbed locking taper. The crack does not extend all the way down into the area where the nut threads engage. BUT: On the other hand, a flywheel that pops off at 5000 RPM is going to do a lot of damage. I doubt that the engine cover could contain it.

Were it my engine, I would first take it to a good machine shop for evaluation, then decide on a course of action. It may just be possible to drill the end of the crack to stop further progression.

Re: 120hp Force crankshaft and stator

If you think about how the flywheel puller works, this may solve the puzzle. The driving bolt is pressed into that 1/2" recess with a wedge shaped pilot, and then someone apply's a little too much 5lb hammer on the end of the bolt to get it to pop. Couple that with possible metal quality issues in the crank, and wallah! instant split. I have never seen this, but have definitely deformed the factory recess more than once trying to get a stubborn flywheel off. I bet this is likely a one in a million type thing.

Frank, the cranks are cast aren't they? If not, I bet a machine shop could weld it up and re-thread it?

Re: 120hp Force crankshaft and stator

I think???The cranks a 1 piece outfit.
Like Tater suggests a puller and a hammer probably did this.
Then like Frank said if it's gonna let go at 5000 and it's gonna hurt.
How far down into the threads does it go?
Depending on how far into the nut it goes.
It probably doesn't go into the taper and it would be ok.
Closer pics???
The first 1/2 to 3/4in aren't used. Possible cut it and then clean up the top for the nut??

Re: 120hp Force crankshaft and stator

tater76 said:

If you think about how the flywheel puller works, this may solve the puzzle. The driving bolt is pressed into that 1/2" recess with a wedge shaped pilot, and then someone apply's a little too much 5lb hammer on the end of the bolt to get it to pop. Couple that with possible metal quality issues in the crank, and wallah! instant split. I have never seen this, but have definitely deformed the factory recess more than once trying to get a stubborn flywheel off. I bet this is likely a one in a million type thing.

Frank, the cranks are cast aren't they? If not, I bet a machine shop could weld it up and re-thread it?

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I suspect you are correct in that the crack is from using the wrong flywheel puller. I had a local boat repair shop do work on the engine about 3 years ago and they were checking the spark. They returned the boat without fixing the problem and told me that it was running fine. When I called them back complaining, they told me that was all they could do and said not to bring the boat back. Now I know why they didn't want me to bring the boat back. They basically ruined my outboard. That makes me mad. They should have known that a flywheel puller for mecury flywheels was needed that inlcudes the cap that goes over the crankshaft end. Though the crack only extends 3/4 inch below the end of the crankshaft and is within the threads and not the taper, I really don't dare just ignore the crack. If the nut breaks of and that flywheel goes to flying, it could do some serious damage to boat and people. Not worth the risk!!!

The problem that got me to finding the cracked crankshaft was the stator. The boat has the "black" stator. Does anyone know about replacing the "black" one with the "red" one? Are there special parts needed, or is it just a straight changeout?

Thanks,

Craig

Re: 120hp Force crankshaft and stator

Should be a straight swap. The black stators seem to fail more than the red ones.

Re: 120hp Force crankshaft and stator

Crankshafts are FORGED with case-hardened bearing journals and crankpins. They can break--I have seen one or two-- but believe me they are tough: I have tried to break off the splined end to make a pinion tightening tool and had to give up. Ruined a good 12 pound sledge and wedge too.

Re: 120hp Force crankshaft and stator

got a new red stator, but the instructions that came with it show a different orientation that does not seem to make sense so now I am trying to figure out if I should try to put it in the orientation that the instructions show, or if I should put it in the orientation that the old one was in which is the orientation the shop manual shows. The dealer told me they no longer sell the black stators and the red ones are the proper replacement. The leads are exactly the same as the old ones and it looks like it should just go in the same orientation as the old one. The confusion comes with the instructions which shows completely different bolt locations. Would you know anyone that has replaced a black stator with a red one?

Thanks,

Craig

Re: 120hp Force crankshaft and stator

The red stator is a generic Mercury stator. It is used for a bunch of different Mercury and Force model engines. Last one I replaced onto a 3 cylinder Merc was marked as to orientation for at least 2 and 3 cylinder engines. I don't remember if it was marked for a 4 cylinder. If your stator is marked, position it as it says. WHEN IN DOUBT, FOLLOW THE INSTRUCTIONS!