98/75 hp Flywheel key

[jerryjerry05]

98/75 Mercury
Keeps shearing the flywheel key.
Starts and runs then makes a noise and shears the key.
4 keys so far.
Nut is torqued to 85#​

 

[Faztbullet]

what type of noise???

 

[jerryjerry05]

Thump,bump. The tapers are smooth.
Clank,clunk.
Then a noise from the starter when it tries to turn the flywheel.
It has good compression.
No chunks or excessive pieces in the oil. New oil.

The magnets in the flywheel had came loose and he ended up taking them out.
Still starts just no charge.

 

[sam am I]

If I had to guess, stator is loose jumping around and jamming into magnets and/or loose magnet/s floating around and jamming into stator..........

Edit, ooops, we posted at same time, never mind on the magnets then. Hmmm.

So the motor doesn't run/work per-se then? You're trying to start it and that's when it thumps and shears? Or it runs a bit and does this?

Maybe a needle/ball bearing and race going to pot and jamming up randomly.

Does the flywheel move left and right if you pull and push on it? Perhaps the main output bearing has been going out for some time and that relates back to why you were having magnet issues earlier? Magnet may have come loose because it hit the stator pole and it hit the stator pole( or has excess vibrations) because the worn bearing is allowing the crank shaft to move around laterally. Just a shot in the dark....

 

[Texasmark]

85 isn't enough. I think my manual said 150 on a 90 hp. You have to have enough torque on the nut to keep the flywheel from slipping on the crankshaft. Any deformation of the key is too much and can causing starting/running problems with timing.

With the magnets out the flywheel could be unbalanced contrbuting to some of the problem.

Since you have to pull the wheel to install another woodruff, give all the wiring and components a good check and check the mounting hardware...look for scrapes and all.

When you get it back together and torqued, grasp the flywheel by hand with the plugs removed and work your way around 360 degrees making 20ish degree advances and then back tracking and then forward and back in a notched fashion, feeling and listening for something loose. You shouldn't be able to feel any play in anything, other than maybe a ring to ring seat change upon changing direction of rotation.

 

[jerryjerry05]

The magnets are gone. Starts just doesn't charg​e.
The taper on the flywheel is scored.
Needs a new one.
Not making a good contact.
150# Sounds like way too much.
Copy and paste the specs. from the manual

 

[Faztbullet]

How does it run with no magnets??? If missing there is no way to generate power for the capacitor in pack......hummm. If owner just removed damaged magnets it could be causing the stator to be out of geometry with trigger. This would cause the capacitor to be fired during the charge pulses. This can result in a induction kick back thru coil to pack causing ignition misfire which could shear key. This is why red stators are marked to which way they mount for the engine they are to be used on.

 

[Texasmark]

The magnets are gone. Starts just doesn't charg​e.
The taper on the flywheel is scored.
Needs a new one.
Not making a good contact.
150# Sounds like way too much.
Copy and paste the specs. from the manual

I would but no longer have the boat nor the manual. Number seemed high to me too but as I recall and the amount causes me to recall it, that is what it said. However, the best thing to do is to get a manual of your own and read for yourself. Don't take my word for it. I am no authority, just attempting to relay past experiences!

 

[Faztbullet]

Flywheel torque is 120ft lbs

 

[jerryjerry05]

Taper on the flywheel is bad.
My memory can and will le​t me down.
So when I post specifics I get my manuals out and make sure I post the right info.
I can't buy a manual on every motor I work on.

Saw a guy give the wrong torque on an exhaust chest reassembly.
Should have been 70in.# (??)guy said 70 ft.#
Stripped some little screws before he figured it out.