Help with flywheel nut size

[schuder]

I made a big Opps, I cleaned up my points on my 1960 evinrude model 35520. That?s the 40hp. I?m putting stuff back together and can?t find the nut and washer. ?Can?t trust kids near the work bench?. So a part # would greatly help. Or just the correct size

 

[bspeth]

0305984 and 0300345

 

[schuder]

Holy CRAP. $18.00 for a nut. How about a hardware store number

 

[jbuote]

Hmmm....
​Maybe a hardware store nut would work with the right threads in it.

If it were me, I think I'd fork over the 18 bucks..

​I'd rather be sure I had the right part, with the right characteristics and reliability than take a chance on potentially inferior materials, hardness, etc...
​Wouldn't want a hardware store nut to strip its threads when applying proper torque..
Even if it held at installation.. Would it loosen up? Shear my flywheel key, possibly causing timing issues which could damage my pistons or worse?

Does it really matter for the flywheel nut? Not sure.. I'm not a trained tech by any stretch.. Hardware store nut may be just fine if it's the right threads and material grade etc...

I guess I'd rather just have the right part in the first place and not have to worry about it, than take any chances..
My 2 cents..
​

 

[F_R]

I think this is what it is, but unsure.
https://www.mcmaster.com/#hex-nuts/=1a5wad7

 

[F_R]

Well that didn't work. Go there and scroll down to "Medium Strength Thin Hex Nuts, grade 5. Then choose size 9/16-18

9/16"-18

7/8"

5/16"

25

94846A530

6.89

Still unsure

 

[Bonaventure]

I think I would rather have Grade 8.

 

[F_R]

I think I would rather have Grade 8.

Probably overkill, but won't hurt. I really seriously doubt the original was Grade 8.

 

[Crosbyman]

i usually find my missing parts after buying new ones ! keep your receipt

 

[jimmbo]

Pay the 18 bucks, you may spend 5 - 10 on gas driving around looking for a cheaper nut, that may or may not be correct.

As for jbuote, "Does it really matter for the flywheel nut?" You really don't want a flywheel coming loose, especially the ones on those old 40s. If it were to come loose, timing issues would be the least of my concerns. But on the brighter side, those old 40s had a pull starter above the flywheel and could withstand the energy if the flywheel tried to climb off. In 74 our 1963 40hp, fresh out of the shop for a tune up, had the flywheel jump up and jammed against the recoil. Flywheel nut had backed off. Either the tech didn't tighten it enough, or snugged it up, went for coffee and forgot to torque it.

 

[oldboat1]

Nearly ruined a '61 Lark by guessing at flywheel torque -- twice. 105 ft. lbs., no less than that -- wouldn't trust anything but the oem nut. $18 is the cost of doing business for resolving that problem (the one you lost will probably turn up unexpectedly, btw, particularly if you buy a replacement -- like Crosbyman says. Add it to your spare parts collection.)

 

[schuder]

I looked all over the shop today and just can?t find them. So looks like I?ll keep my eyes open for one. Thanks for the help. Would placing a little silicon on the threads above the nut after torquing it down to 105 # be a good or bad idea ?

 

[F_R]

Why?

 

[schuder]

Other people say the nut could still back off making a bigger problem

 

[oldboat1]

Nah. Torque will do it (tapers will hold it) May discover that when you want to pull the wheel again in a few years.

Use some acetone or similar on the shaft before assembly to make sure there is no grease or oil.