Currently undertaking an opportunistic antifoul and am changing the cutlass bearing while on the hard. So I cant get a 3/4 brass castle prop nut anytime soon and the current one is a bit shot but I have got a brand new brass nyloc nut in my hands. Do any members see any known problems with using a new nyloc?
Nyloc brass prop nut or not ??
- Thread starter Brahmany
- Start date
Brass is usually not recommended for use below the waterline. It degrades too quickly. If it fails, it will do so at a most inopportune time and you'll be out the nut and perhaps a very expensive prop.
I wouldn't trust a nylok, or brass (in salt water?) for that. Bronze on a bronze shaft or stainless on stainless. But definitely use a cotter pin, same material as the shaft and nut. If you can't get a castle nut, maybe you can file a notch in the nylok to take the cotter. Amounts to the same thing.
I'm with those above who would advise you against both the brass and the nyloc. I don't think a bit of plastic should be anywhere in your running gear. Buy a SS or bronze nut and if necessary have the yard drill a hole for the cotter key. You'll be much more relaxed when motoring.
So I just replaced my old bronze shaft with a new SS shaft. I cleaned the bronze prop nut and lock nut and planned to reuse those. I also have a bronze prop.
I am am in fresh water (Lake Michigan). Do I need to replace the bronze prop nut to SS ?
Going to launch in a week...
Greg
I am am in fresh water (Lake Michigan). Do I need to replace the bronze prop nut to SS ?
Going to launch in a week...
Greg
No, your bronze nut will be fine. Invest in a new cotter pin to hold it all together.
The issue is that bronze and brass, while similar, have very different properties in terms of corrosion and strength. Bronze is stronger and less susceptible to corrosion. Not so much with brass.
Replace the shaft anodes with aluminum not zinc. Too many freshwater boaters use zinc, should be aluminum or magnesium.
The current thinking is that Aluminum is good for fresh or saltwater.
www.boatzincs.com/pdfs/Chart_B-Which_Anodes_Should_I_Use.pdf
#1 Avoid SS nuts because thread galling can ruin a prop shaft and the nuts. I've seen this more than once $$$$$. This is why you see so few SS prop nuts. Also shafts are not really a typical 304 or 316 SS, nor should they be, they are in the stainless family but not typical SS but they are still prone to thread galling..
#2 Prop nuts are technically "brass" not a true bronze. Almost all of them, unless you source from a disreputable supplier, are "Manganese Bronze". Manganese bronze is really only a bronze by name not by composition. Technically manganese bronze is a brass but it's not a low grade Home Depot "yellow brass" consisting of only copper and zinc.. The nuts are usually made from the C86500, C86200 or C86300 metallurgy, the same metallurgy used in the vast majority of props. Of course because "manganese bronze" is not really a bronze, like good seacocks are made from, and the nuts and prop will rely on your anodes for protection.
"Brass" prop nuts are used because they are essentially self lubricating (no thread galling) and they match or closely match the alloy of most props. Standard yellow brass nuts are not the same as a C86500, C86200 or C86300 manganese bronze/brass so the two should not be confused. Unless you can confirm the metallurgy of a "brass nut" stick with nuts made for prop shafts and purchase them only from reputable prop shops.
#3 Nyloc prop nuts are widely used on ski boats and outboard motors, backed up by a cotter pin. Most of these applications have significantly more HP than our boats do. A castellated nut is still preferred over nyloc, if that is what the prop shaft was cut for, but a king nut (full height nut) and jam nut (half height nut) and cotter pin are the industry standard procedure.
#2 Prop nuts are technically "brass" not a true bronze. Almost all of them, unless you source from a disreputable supplier, are "Manganese Bronze". Manganese bronze is really only a bronze by name not by composition. Technically manganese bronze is a brass but it's not a low grade Home Depot "yellow brass" consisting of only copper and zinc.. The nuts are usually made from the C86500, C86200 or C86300 metallurgy, the same metallurgy used in the vast majority of props. Of course because "manganese bronze" is not really a bronze, like good seacocks are made from, and the nuts and prop will rely on your anodes for protection.
"Brass" prop nuts are used because they are essentially self lubricating (no thread galling) and they match or closely match the alloy of most props. Standard yellow brass nuts are not the same as a C86500, C86200 or C86300 manganese bronze/brass so the two should not be confused. Unless you can confirm the metallurgy of a "brass nut" stick with nuts made for prop shafts and purchase them only from reputable prop shops.
#3 Nyloc prop nuts are widely used on ski boats and outboard motors, backed up by a cotter pin. Most of these applications have significantly more HP than our boats do. A castellated nut is still preferred over nyloc, if that is what the prop shaft was cut for, but a king nut (full height nut) and jam nut (half height nut) and cotter pin are the industry standard procedure.
There seems to be universal agreement that Magnesium should not be used in salt or brackish water and zinc doesn't work in fresh water.
I've used both magnesium and aluminum in freshwater and after a season there is very little difference in how much the anode has sacrificed. As I understand it, some magnesium is contaminated with cadmium that leaches into the water, aluminum does not have the same issue. And aluminum is a few dollars cheaper.
The other caveat is that you don't mix and match, pick a type and stay with it.
Thanks Dave,
New magnesium anode is already on, new SS cotter pin is ready to go after I recheck the nut tightness this weekend.
I see some other good info below, so thanks all for the confirmation.
Scheduled my launch fora week from Saturday! New marina docks and layout at my marina (hence the delayed opening), should be exciting !
Greg