Roger Long
Senior Member
When we hauled our boat to return home for the holidays in December, I was surprised to find one of the prop castle nuts loose. The wheel was tight on the shaft and the cotter pin was in so I figured there must have been a slip up when the drivetrains were overhauled a year earlier. I tightened it up almost a full turn and just barely got the cotter pin back in the groove.
We hauled again a couple weeks ago and were leaving the yard racing darkness and the big northeaster for our drive north . I looked at the prop nuts as I walked to the car and was surprised to find the same nut loose with the pin properly inserted. There was perhaps 1/8” in between the nut and hub. The light was bad but the nut felt and looked odd. Our zincs have been going quickly so I have some electrical things to check out but I was also wondering if this boat that was always in fresh water until our ownership might have a brass prop nut. The best thing at that point seemed to be to deal with it when we get back to VA to paint the bottom and re-launch
Anyone have thoughts on how the nut could get loose twice without getting physically smaller through corrosion? I’m sure the prop has not slid up the taper.
Now that I’m thinking about the schedule when we get back to the boat, I don’t want to be spending another day on the shaft so I’m looking around for a prop nut. I was surprised to find this:
https://www.passagemaker.com/channels/propeller-nut-myth-busting
It says:
Poll: Should I order a brass or bronze shaft nut? Both seem to be available.
We hauled again a couple weeks ago and were leaving the yard racing darkness and the big northeaster for our drive north . I looked at the prop nuts as I walked to the car and was surprised to find the same nut loose with the pin properly inserted. There was perhaps 1/8” in between the nut and hub. The light was bad but the nut felt and looked odd. Our zincs have been going quickly so I have some electrical things to check out but I was also wondering if this boat that was always in fresh water until our ownership might have a brass prop nut. The best thing at that point seemed to be to deal with it when we get back to VA to paint the bottom and re-launch
Anyone have thoughts on how the nut could get loose twice without getting physically smaller through corrosion? I’m sure the prop has not slid up the taper.
Now that I’m thinking about the schedule when we get back to the boat, I don’t want to be spending another day on the shaft so I’m looking around for a prop nut. I was surprised to find this:
https://www.passagemaker.com/channels/propeller-nut-myth-busting
It says:
Not using brass on critical items below the waterline has always been religion. The prop nuts I've always had before sure looked like bronze to me and not brass.Yes, that’s right; the alternative (and I would argue a preferred one to stainless steel propeller nuts) is brass, and any propeller nut you see that isn’t stainless steel almost certainly is, contrary to popular belief, brass rather than the erroneously assumed bronze. While I admonished readers about the use of brass in a previous column, this is an exception to that rule.
Brass, actually manganese bronze (which is a misnomer, as technically, this alloy is in the brass family), is used for a few reasons. As mentioned, it’s especially slippery, thereby protecting your valuable propeller shaft threads from galling. Brass is strong and relatively easy to machine, making it well-suited to the manufacture of nuts. Finally, many propellers are made of manganese bronze (again, that’s technically brass) and as such, a genuine bronze nut would be cathodic to the prop, making the latter more likely to corrode when the two were in contact. If you maintain your shaft anodes, propeller and nut corrosion should never be an issue. Thus, when specifying a replacement propeller shaft, or just replacement nuts, go for the brass.
Poll: Should I order a brass or bronze shaft nut? Both seem to be available.