Broken bolt in flywheel

[Evinrude Boater]

One bolt for the coupler broke off in the flywheel. I've soaked it and cleaned out the exposed threads but I can't get it to budge either way. Should I be concerned about removing it or just rotate the coupler to another set of holes and leave the broken bolt.

 

[Aloysius]

Re: Broken bolt in flywheel

Theoretically it will cause a balance problem, but in reality you'll never notice it. Clocking the coupler is ok IF you have holes that work.

 

[wire2]

Re: Broken bolt in flywheel

If you HAVE to get it out;

If it's broken off below the surface, an easy-out or a left handed drill are 2 possibilities.

If it's flush, or slightly above, place a same size flat washer on it, then an oversized hex nut. Tig weld the inside of the nut to the stud. The washer stops the weld from arcing to the flywheel, the weld heat will expand the stud.
Let it cool and it shrinks, usually allowing fingertip removal.

 

[mkast]

Re: Broken bolt in flywheel

If it's a "through hole", bolt hole goes all the way through the flywheel, remove the flywheel, turn the flywheel around, center punch the broken stud and drill through the stud, use smaller bit.
The action of the drill bit turning should "walk" the stud out.

 

[Evinrude Boater]

Re: Broken bolt in flywheel

The bolt is broken off below the surface. I drilled it through and used a removal tool from both sides and was only able to back it in a few budges even when heating the flywheel with a propane torch. I thought I could screw it through the flywheel if I cleaned and lubricated the exposed threads in the hole. I guess the threads are all tightened up with rust where it stopped turning. It appears to have another set of holes for the coupler. If worse comes to worst, I'll run a tap through them and use them for reassembly. I suppose I can drill it out more to lose some weight to avoid a balance issue.

 

[Bondo]

Re: Broken bolt in flywheel

even when heating the flywheel with a propane torch.

Ayuh,... Heat the broken Bolt, not the flywheel,... Then Quench it with water...
And,...
Propane ain't hot enough to do squat,... Try Mapp or Ox/Ac...

 

[coheej]

Re: Broken bolt in flywheel

As bondo says heat the bolt not the flywheel. I try to heat it until the bolt just starts to glow slightly and then quench with wax or oil. Let it cool and usually it backs out easily. If you use a flamable or like wd 40 it will flame up if you're not careful.

If you don't get it out, the out of balance shouldn't be too far off. A 1/2" long piece of 3/8" bolt probably weighs about 5 grams. This weight is at the outside edge of the flywheel or about 7" from center. At the counterweight area of the crank where you normally do the weight adjustments, this would be about 10 grams out of balance. If you've drilled the center out, this may be back down to 5 or 6 grams. The flywheel was probably off that much to begin with.

 

[Evinrude Boater]

Re: Broken bolt in flywheel

I got the bolt out by drilling it as large as I could and using the biggest screw extractor that would fit. It's times like this that I wish I had a set of torches.