terry_thatcher
Terence Thatcher
When I purchased my 382 28 years ago, the prior owner had installed a shaft brush. That is, because of a flexible coupling that electrically disconnected the engine from the shaft and prop and shaft log, there is a "brush" that rubs on the stainless shaft and a wire running from that "brush" to a bolt on the engine. I have kept it all these years.
But, I now question its necessity or wisdom. The various metals on the Morgans (chain plates, through hulls, etc) are not "bonded." (Maybe not a great idea for a Florida boat, but . . .) All my through hulls are bronze. My prop is bronze. My cutlass bearing and shaft log are bronze. My gudgeons are bronze. The only dissimilar metals under water are the stainless shaft and the stainless rudder post. (I am thinking about going to a bronze shaft, but that might require a larger diameter, which complicates things immensely.) I run a zinc on my prop and before the big MaxProp, I had an additional shaft zinc. (I may try to find a smaller one to put on the shaft in front of the prop again.)
My main DC negative ground is my battery bank. The engine starting motor is grounded there. I have a galvanic isolator and an ELCI on my AC system.
So, what is the shaft brush doing except connecting the engine to my shaft, which might just encourage increased wasting of the prop zinc and mild steel of the engine components? Or even encourage wasting of the engine anode, which is an issue on Beta engines.
I have read all about how to "bond" a boat and, if done well, it might provide a way to protect against lightning strikes (although from my reading, I doubt it). But, on an unbonded boat, should I discard the shaft brush? If I remove it, the shaft and prop etc will no longer be connected electrically to the engine and the battery negative. OR should I keep it? And why? Would the ABYC standards answer this? Jim Cleary, your thoughts are particularly invited.
Thanks for any thoughts.
Forgot to mention, my new ZF transmission has a cooler, just a bolt-on aluminum box, thru which salt water from the engine system circulates. That may be subject to corrosion, of course. Does that change the analysis? Maybe it adds to the engine zinc load.
But, I now question its necessity or wisdom. The various metals on the Morgans (chain plates, through hulls, etc) are not "bonded." (Maybe not a great idea for a Florida boat, but . . .) All my through hulls are bronze. My prop is bronze. My cutlass bearing and shaft log are bronze. My gudgeons are bronze. The only dissimilar metals under water are the stainless shaft and the stainless rudder post. (I am thinking about going to a bronze shaft, but that might require a larger diameter, which complicates things immensely.) I run a zinc on my prop and before the big MaxProp, I had an additional shaft zinc. (I may try to find a smaller one to put on the shaft in front of the prop again.)
My main DC negative ground is my battery bank. The engine starting motor is grounded there. I have a galvanic isolator and an ELCI on my AC system.
So, what is the shaft brush doing except connecting the engine to my shaft, which might just encourage increased wasting of the prop zinc and mild steel of the engine components? Or even encourage wasting of the engine anode, which is an issue on Beta engines.
I have read all about how to "bond" a boat and, if done well, it might provide a way to protect against lightning strikes (although from my reading, I doubt it). But, on an unbonded boat, should I discard the shaft brush? If I remove it, the shaft and prop etc will no longer be connected electrically to the engine and the battery negative. OR should I keep it? And why? Would the ABYC standards answer this? Jim Cleary, your thoughts are particularly invited.
Thanks for any thoughts.
Forgot to mention, my new ZF transmission has a cooler, just a bolt-on aluminum box, thru which salt water from the engine system circulates. That may be subject to corrosion, of course. Does that change the analysis? Maybe it adds to the engine zinc load.
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