What size nut on a 90hp flywheel ?

Im looking for the right socket to take the flywheel nut off a 90hp flywheel.
My biggest one is 24mm, and im thinking its either 26 or 27mm.

Anyone with info ?
Thanks

Re: What size nut on a 90hp flywheel ?

How high is high? How far is far? It really would save time to know the engine year. Chrysler and early Force used a 1 1/16. Sometimes on these older engines you will find a "bastard" nut such as 1 1/8. In fact I did you a favor and ran down to the garage. The only Merc flywheel nut I have is just shy of 1 1/8. Close enough that you could use a six point socket on it. Didn't have my big metric sockets or metric ruler handy though. If you absolutely need metric, I would go with 28 as conversion chart shows 1.122 ( 1/8 is .125) inches as 28.5 mm

Re: What size nut on a 90hp flywheel ?

its a 1994 Force Merc 90hp. I thought they used metric then ? I guess 1 1/8 sounds right. Thanks for checking, Frank.

Re: What size nut on a 90hp flywheel ?

1 and 1/16 th I believe.J

Re: What size nut on a 90hp flywheel ?

1 1/16th is the perfect fit for me. I dont have the "bastard" nut, lol. But now im facing the next problem is to yank it off. I used a gear puller from Autozone and its not even moving. I guess its the cold weather which causing the metal to shrink. I read from somewhere that torching it will help loose the grip.

Next question is whether it's okay to replace it with a compatible flywheel ? I have a flywheel from a 120hp engine, but as far as balance I dont know if it will work with the current crankshaft which only have 3 cylinders instead of the original 120hp4cylinders.

If anyone have replaced their flywheel with another one and it worked fine, let me know. Thanks.

Re: What size nut on a 90hp flywheel ?

There is no problem with balace: All flywheels are dynamically balanced by the manufacturer before installation on the engine. Pistons and rods are balanced by the craknshaft cheeks.

All three and four cylinder engines used the same flywheel until Merc started putting on their ignition. Even then, I think Merc used the same flywheel for 2,3,and 4 cylinder engines. Use a steering wheel puller or harmonic balancer puller and thread three 1/4 X 20 bolts into the holes on top of the flywheel. If you have an impact air gun they will usually pop the flywheel quite nicely. If you do not have one, torque the center bolt really tight and smack the top a few good shots with a heavy hammer--16 oz will not do. If that doesn't do it, use a propane torch and heat the center of the flywheel. She will jump up with a bang.

Re: What size nut on a 90hp flywheel ?


I use a BIG 3 jaw puller an impact wrench and a 2/3# hammer.See pic.
Loosen nut,don't remove all the way.
Insall puller and tighten as tight as it will go and then a bit more.
Then hit with a hammer on the end of the puller bolt.
Use gloves and keep your hands away.It will come off with FORCE!!!
That's why you leave the nut on.
I don't like to use heat as you can ACCIDENTLY melt the top crank seal.

Re: What size nut on a 90hp flywheel ?

I used the exact gear puller like JerryJerry. It was a loaner tool from Autozone But after a careful inspection of the two flywheels, the 90hp I have got a smaller crank shaft than the 120hp flywheel. I think its because the 120hp flywheel was from the '96 model which then they changed a few things. The 90hp flywheel is from a '94 engine.

But I found that out a bit too late after I have taken a magnet from the 90hp flywheel and JB welded onto the 120hp flywheel. Now im missing two magnets-one broke in half.
Im now hunting for a new set of magnets after new year.

Have A Happy New Year!