special nuts required or not?

[topseaturvy]

I have a 37 Trojan with 454 Crusader gas engines. I'm in the process of cleaning out the exhaust/heat exchanger of all the corrosion build up.
The nuts called for that hold the 8" elbow (cr-20-97169) ( sierra 18-1916) to the exhaust manifold are 3/8" coarse brass heavy with nyloc. Heavy meaning instead of a 9/16" socket you need a 11/16" socket. I've searched all of North America for the nuts and washer sets (sierra 18-8540) and I've only found one place on Long Island that has them, but they won't ship to Canada. But I've tracked down a brass nut with nyloc that is standard size ( 9/16" socket). I've also tracked down a "heavy" brass nut without the nyloc. I've found them both locally.
My question is, why does crusader call for this heavy nut?
I'm only applying a max of 20 ft. lbs. torque, so I don't think it is for strength. I'm guessing it's maybe to distribute more surface area of pressure on the copper washer. My guess is that the copper washer is used as a gasket to keep the salt water from escaping out along the stud and then from escaping between the casting and the under side of the washer.
I'm guessing the nyloc is needed to keep the nut from loosening off. Perhaps also to keep any salt water that would get past the inside diameter of the copper washer and the stud and try to work it's way out the end of the threads.
I could use that heavy nut without the nyloc and a brass lock washer, plus thread sealant, but maybe the copper is too soft and the lock washer would just not get a good foothold to prevent the nut from loosening. Which might be the reason why they went with a special nut with nyloc
Any thoughts or experiences with this?

[WayWeGo]

You should check with Bob at Beacon Marine. His cell phone number is 609-713-4602. He is a fantastic resource for Trojan owners!

[prowlersfish]

I would not worry much about the special nuts , You will find more manifolds and risers put together with regular nuts and bolts then not . keep good paint on them .

[P-Dogg]

I would not worry much about the special nuts , You will find more manifolds and risers put together with regular nuts and bolts then not . keep good paint on them .

^^^This. And I have become a big fan of nuts with integrated washers, a.k.a flange nuts. Use whatever will withstand the (modest) torque and be done with it, but don't skip the copper washer. Nice to see someone trying trying hard to keep it spec, though.

[ken64k]

I found this site that has them

https://www.marineengineparts.com/sierr ... aust-riser

[topseaturvy]

I found this site that has them

https://www.marineengineparts.com/sierr ... aust-riser

Thank you for looking ken64k. Yep that's the same place where I found them too. They're at the far end of Long Island NY. The only place actually that has them that I could find. They say that they have lots of stock but they won't ship to Canada. They won't even accept my visa credit card over the phone for payment. They say they need paypal as a payment method. There are a few places that have the nut/washer set on their website but when I call or email, I find out they no longer carry them.

[mikeandanne]

If you are just looking for brass locking nuts and washers, try Fastenal Canada, lots o stuff.

[topseaturvy]

If you are just looking for brass locking nuts and washers, try Fastenal Canada, lots o stuff.

Yes I tried Fastenal and they'd never heard of such an odd ball nut.

[mikeandanne]

I thought it seemed a bit odd, but these are on their website to order.

https://www.fastenal.ca/productList/Fas ... s&toggle=0

[topseaturvy]

I thought it seemed a bit odd, but these are on their website to order.

https://www.fastenal.ca/productList/Fas ... s&toggle=0

Those nuts are not the ones I'm looking for. I need what's called a "heavy" nut. So instead of using a 9/16" wrench/socket, you use a 11/16" wrench/socket. Yes heavy brass 3/8" coarse nuts are available from some suppliers, but not with the nyloc insert.

[mikeandanne]

Aha, I see now, I'm old and cant read

[topseaturvy]

Aha, I see now, I'm old and cant read

I appreciate the effort you went to in trying to help me with this dilemma mikeandanne.
I also appreciate everyone else's input as well

[WayWeGo]

That's what makes this site so great -- I would never have bought our F-36 without knowing I would have support keeping her running.

The friendships I have made with the members is a big bonus!