Help with flywheel bolt size for pulling

[kaupinator]

I am trying to pull the flywheel off of a 1969 85hp evinrude. I bought 3 grade 8 5/16in bolts. They seem to be stripping the threads on the flywheel when I try to screw them in for the puller. What is the correct size? I saw several posts with grade 8 1/4in. but those are way to small. Help!

 

[Cap'n Chaos]

Re: Help with flywheel bolt size for pulling

If the threads are stripped... you're going to have to tap them.

Somebody here with more experience may offer a better solution.

 

[mikesea]

Re: Help with flywheel bolt size for pulling

they are a finer thread ,you need 5/16 24 ,not the course 5/16 18

 

[kenmyfam]

Re: Help with flywheel bolt size for pulling

Standard 5/16" thread has 18 threads per inch.
Fine thread 5/16" has 24 threads per inch.
Stripping the flywheel threads......Oh Dear !!!
You may well need to drill and tap them out to 3/8" or even 7/16" thread.

3/8" fine thread needs a letter "Q" tap drill at 0.332" diameter, then tap it out with a 3/8"-24 TPI bottoming tap.
A substitute drill for this one would be a 21/64" and that is 0.004" smaller in diameter.

7/16" fine thread needs a 25/64" drill and a 7/16"-20 TPI bottoming tap.

Coarse threads give less pulling power before stripping out for things like flywheels etc.
Good Luck.
Ken.

 

[boobie]

Re: Help with flywheel bolt size for pulling

Get a 5/16-24 tap and run down through the holes but not to far as you may hit some electrical component under the flywheel. Then try the new correct bolts with your puller. I've had this happen to me and if the holes were stripped I'd just heli-coil them. All the holes may not be bad. To me it beats beats drilling them all out over size. Besides the heli-coil will be stronger than the orginal threads anyway.

 

[kenmyfam]

Re: Help with flywheel bolt size for pulling

Besides the heli-coil will be stronger than the orginal threads anyway.

???????

 

[bktheking]

Re: Help with flywheel bolt size for pulling

So they say, the key is getting them installed perfectly.

 

[boobie]

Re: Help with flywheel bolt size for pulling

Kenmyfam : I didn't quite get your last post ????