The drawback of stainless steel, wet and encased, crevice corrosion develops and stainless fails on itself. I'd bet, pull those screws and a few will be black. I do not know how to test them reliably with out just replacing them.
cleanslate, really good point. I will pull and replace a few as suggested by CR to see if I have an issue. Also, I don’t know the material used for the trim tabs. The anodes on the tabs wear out much faster than all the others zincs. Wonder if the tabs are something other than stainless and reacting with the screws. Hope this does not turn into a boat$ project. Spring project is trolling valves.
Mine go way back to 1981 mine stayed in on the bottom water side and did not leak luckily and all are not bad.; Yours looked ok, but you never know. If broke pull them and re install with S/S again or silicone bronze , if you can find machine bolts that size. But I think the trim tab is perhaps bronze sheet..darn if I know. I will sand one of mine down ( remove the bottom paint) while I'm out to see.
No they are not, they are protected by a zinc on their own. I'm not bonding mine. Still there after 40 years and they work just fine. I've got plenty of other stuff to do on my Ocean ''not'' Yachts.
Bottom of the bottom pic in post #38 shows your bonding wire. On our Bertram, The factory 42 years ago used stainless on all underwater items except for the bonding wire connect, it was bronze. Lower wet electrical resistance. It had zincs on the trim tabs when we purchased it, still use them (zincs) now. Bonded or not, zincs on a trim tab seems to always be a good idea, as long as there was a hole drilled for it. Tabs are usually made of stainless steel.
That is good to know. Of course S/S tab, S/S fasteners.....You can drill your own hole if one is not there. Like my rudders....that will change soon. Anyway Capt Ralph, how's it hangin'? Things doing Ok?
Embarrassed my self well yesterday on another thread. Took a couple of pain pills and wrote a page of stuff with examples. When questioned on it by a friend later in the day, I re-read it; what a bunch of nonsense I typed. So, I am well, new hip doing well, therapy doing well, back doing better but mind not working well with new drugs. Thanks to all for your good thoughts, vibes and prayers.