Bronze Motor Mounting nuts

[croaker stroker]

Just looking into things and made a discovery.

The bottom nuts holding my outboard to the transom are Bronze 1/2" - 20 Nyloc.

The threads are perfect. Since these nuts look like they may have survived 37 years of saltwater use, I decided that I wanted to replace them with new bronze nuts. The guy who is installing the motor said they only use stainless steel.

I thought I would be smart and source the bronze Nylocs, but I have looked everywhere and can't find them.

I will keep looking, but does anybody know who might carry these nuts ?

They may have originally been chrome plated as the port side still has a bit of chrome that hasn't dissolved through the years.

[Tom C]

They are not bronze, they are brass. Mercury uses them to prevent galling. Because they are fine thread, they are almost impossible to find any place other than a Mercury dealer.

There is nothing wrong with using stainless steel nylocks, but you should use some grease, or anti-seize (for stainless) on the threads. Having a nut gall on a bolt is no fun.

https://www.boats.net/product/mercury/82671117

[fishmeister]

Croaker asking a question about nuts.  What could possibly go wrong on this forum?   

[croaker stroker]

They are not bronze, they are brass. Mercury uses them to prevent galling. Because they are fine thread, they are almost impossible to find any place other than a Mercury dealer.

There is nothing wrong with using stainless steel nylocks, but you should use some grease, or anti-seize (for stainless) on the threads. Having a nut gall on a bolt is no fun.

https://www.boats.net/product/mercury/82671117

I don't know how you can tell what metal they are by looking at a photo? They are definitely bronze color. 

I brushed them with a wire brush and could not scratch them. If they are brass, they are the hardest, most difficult to polish brass that I have ever encountered. 

[Tom C]

If you follow my link above, you'll see that Mercury calls them brass, therefore I assume they are made of brass.

I have a very small diamond grit arbored disc I chuck in my drill press when I want to shine small metal hardware up. Works great on these nuts, but I will warn you: I would not reuse those nuts if they are really that old. They can split in time, and the fractures are hard to see. You've been warned.

[Edit: The boats.net link does not call them out as brass, this one does: https://www.partsvu.com/nut-500-20-1.html Better price too. ]

[Tom C]

I brushed them with a wire brush and could not scratch them. If they are brass, they are the hardest, most difficult to polish brass that I have ever encountered.

Yes, that is why they cost $8 each.

[Keel-er]

There are a few different brass alloys that vary in color and hardness.  We're having to switch a lot of our instruments to C69300 brass to comply with medical regulatory requirements for no lead and that stuff.  Our machinists tell me it's hard like stainless.

[croaker stroker]

If you follow my link above, you'll see that Mercury calls them brass, therefore I assume they are made of brass.

I have a very small diamond grit arbored disc I chuck in my drill press when I want to shine small metal hardware up. Works great on these nuts, but I will warn you: I would not reuse those nuts if they are really that old. They can split in time, and the fractures are hard to see. You've been warned.

[Edit: The boats.net link does not call them out as brass, this one does: https://www.partsvu.com/nut-500-20-1.html Better price too. ]

They were originally chromed.

I have used a lot of Perko hardware. That's why I thought they were chrome plated bronze...that and the copper color and hardness.

Good point regarding the splitting.

Guess I'll have to submit to the Stainless....Or the Mercury part. (Thanks for the link.)

[Tom C]

I am sure the nuts were not chromed. Mercury never did that, nor do they do that.

[croaker stroker]

I am sure the nuts were not chromed. Mercury never did that, nor do they do that.

Port side still has some chrome with the "mystery metal" underneath.

Guess that rules out Mercury.

[Tom C]

Well, that sure looks like chrome or nickel plated brass or bronze to me. I have never seen one holding an outboard on a boat. It also looks like it has some fractures in it.

[AJFishin]

Maybe someone got created after installing them. 

[Tom C]

Who knows? It's a moot point; at that age, new nuts should be used.

I also recommend an SAE washer be used under each of the four motor mounting nuts, whatever they are made of.

It is not unusual for a boat made in the 1980s or 1990s that has been repowered to have the motor mounting bolts reused. This may, or may not, be OK. I removed a 1988 Mercury 80 over the weekend and the 1/2" stainless steel mounting bolts showed visible erosion of the shank diameter near the exterior of the transom thickness. They went into the recycle bin.

[Tom C]

Historically, here is what the major outboard manufacturers provided for mounting their outboards:

Mercury used 1/2" - 20 stainless steel bolts with brass nylocks

OMC/BRP used 1/2" - 13 stainless steel bolts with stainless steel nylocks

Yamaha used 12mm high strength steel (HSS) bolts with doubled up hex nut (not nylocks)

[croaker stroker]

Well, that sure looks like chrome or nickel plated brass or bronze to me. I have never seen one holding an outboard on a boat. It also looks like it has some fractures in it.

I am not planning to re-use them. They are probably 37 years old. Used in salt water their entire life. The nut outlasted the chrome. They don't make 'em like that anymore.

Anything I buy today probably wont survive that long..... but neither will I. 🥴

[Fisherdv]

Maybe that's a good case of "if it ain't broke, don't fix it ".

[croaker stroker]

Maybe that's a good case of "if it ain't broke, don't fix it ".

I wonder why they didn't use a nut like this on the bow eye?

[Hydroman]

I expect the nuts are NAVY BRONZ, we used then on all SS bolts that were underwater at dams that I worked at. You should be able to find them at most industrial fastener suppliers. The problem you might have is finding someone to just sell you a couple of them.

You might want to check the size of the propeller shaft nuts on some the small outboards, I believe most of the are brass nylock.

Jim

[croaker stroker]

I expect the nuts are NAVY BRONZ, we used then on all SS bolts that were underwater at dams that I worked at. You should be able to find them at most industrial fastener suppliers. The problem you might have is finding someone to just sell you a couple of them.

You might want to check the size of the propeller shaft nuts on some the small outboards, I believe most of the are brass nylock.

Jim

I did find bronze nylocs, but they were 1/2"-13 and I need 1/2"-20. I failed at finding the fine thread.

It is just annoying that I can't find them. The 316 stainless will out-live me.

I have to admire the quality of some materials Arima used. When I replaced the wood panels on both boats, I was shocked to find the Teak lumber core plywood and phenolic (similar to Formica) laminate.

[croaker stroker]

There were Stainless Steel washers behind the nuts and there is corrosion on the motor mount. (See pic)

I wonder if the corrosion was caused by the stainless washer?

Would a bronze washer react with aluminum less than Stainless?

....Strramfixer would say I am "picking the flyshit out of the pepper" 😂

[Tom C]

The corrosion is normaal. Saltwater makes it worse, as does dirt.

Remember, outboard motors are essentially aluminum parts held together with stainless steel nuts, screws, and washers. No need to overthink it.

[Wiley]

Grainger industrial supply ?

[croaker stroker]

Grainger industrial supply ?

No bronze nylocs. I did find bronze 1/2-20 hex nuts on EBAY, but I would have to use jam nuts.

[Wiley]

?asked google ?

[croaker stroker]

I ordered some bronze washers on EBAY, and 316 Stainless Nylocs.