Upon hauling my 1983 Hunter 31 I wasn't surprised to find the prop shaft's cutlass bearing needed replacing, but in doing so what I discovered was a bit frightening. There is a brass flange or fitting surrounding this through-hull opening, through which passes the shaft with the cutlass bearing. Upon removing the packing this brass fitting was heavly fractured with large pieces missing. The fitting's metal center now exposed because of the broken pieces showed the metal to be completely pink from electrolysis all the way through. Pieces of the fitting crumbled as it was being removed. This was frightening as this was the only thing between the boat's interior and the ocean. The boatyard mechanic said this was the third Hunter of this size and age wherein he's discovered this same condition during the past three months. He didn't even attempt locating a new part, and just constructed one out of stainless. I'd caution other Hunter owners who haven't had the packing removed and this fitting examined to do so. If it's as bad as mine was it'll be obvious to the eye.
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Shaft Log?
I just replaced one on another boat (not Hunter). If it is electrolysis, you should be aware the shaft can be bad too and look OK from the outside. Stary currents in marinas can melt logs, shafts and props plenty quick unless good zinc control is maintained. Rick D.
I just replaced one on another boat (not Hunter). If it is electrolysis, you should be aware the shaft can be bad too and look OK from the outside. Stary currents in marinas can melt logs, shafts and props plenty quick unless good zinc control is maintained. Rick D.
Doubt that it is a Hunter problem.
Scott: I doubt that this is unique to Hunter. I think you will find that it has more to do with boats that came out of HOT harbors. Like Rick says, stray current can be a real problem.
Scott: I doubt that this is unique to Hunter. I think you will find that it has more to do with boats that came out of HOT harbors. Like Rick says, stray current can be a real problem.
Thru Hull? Shaft Log?
I'm not sure what thru hull you are talking about, but I recently posted a similar problem. At launch this spring, the yard noticed a bad leak at the shaft log on my 1980 Hunter 30. After removal of the engine, stuffing box and shaft, the bronze shaft log fitting was noted to be fractured along its length. The yard commented that it came apart in pieces and appeared to have been that way for a long time based upon what they described as water staining and corrosion within the crack. I don't know what was holding it togther. The piece was replaced with a custom turned $tainless $teel fitting. The fracture seemed unrelated to alignment, vibration or other such causes. It could have been due to electrolysis but I have not noticed any such problem with my prop, shaft, other thru hills or shaft zincs.
I'm not sure what thru hull you are talking about, but I recently posted a similar problem. At launch this spring, the yard noticed a bad leak at the shaft log on my 1980 Hunter 30. After removal of the engine, stuffing box and shaft, the bronze shaft log fitting was noted to be fractured along its length. The yard commented that it came apart in pieces and appeared to have been that way for a long time based upon what they described as water staining and corrosion within the crack. I don't know what was holding it togther. The piece was replaced with a custom turned $tainless $teel fitting. The fracture seemed unrelated to alignment, vibration or other such causes. It could have been due to electrolysis but I have not noticed any such problem with my prop, shaft, other thru hills or shaft zincs.
What else was Impacted?
I had a similar situation several years ago when electrolysis occured; I presumed, from a nearby boater having left a live 120V power cord plugged in and under water in his slip. My first notice of a problem was the next fall when a strut was 'pink', slightly deteriorated and needed to be replaced when the marina relplace a a worn cutlass bearing. I later found a gate valve valve stem corroded thru to nothing, but other seacocks and thru hull fittings appeared OK. Another couple years later I found one of the bronze thru hulls had noticeable voids in it's outer flange and I replaced it. There seemed to be no problem with the bronze shaft or bronze folding prop, but I routinely have used two zincs on the shaft since the original incident. I fitted a new shaft log and bronze stuffing box 3 years ago and did not notice any deterioriation of the bronze thru hull portion of the original shaft log. Is there any non-destructive way to determine the soundness of the bronze thru hull components? On my 28.5, none of the thru hulls, nor the strut are bonded or grounded, though, presumably, the shaft , prop, zincs and engine are all in contact with each other. Any sage observations from the knowledgable electrical engineers in the group?
I had a similar situation several years ago when electrolysis occured; I presumed, from a nearby boater having left a live 120V power cord plugged in and under water in his slip. My first notice of a problem was the next fall when a strut was 'pink', slightly deteriorated and needed to be replaced when the marina relplace a a worn cutlass bearing. I later found a gate valve valve stem corroded thru to nothing, but other seacocks and thru hull fittings appeared OK. Another couple years later I found one of the bronze thru hulls had noticeable voids in it's outer flange and I replaced it. There seemed to be no problem with the bronze shaft or bronze folding prop, but I routinely have used two zincs on the shaft since the original incident. I fitted a new shaft log and bronze stuffing box 3 years ago and did not notice any deterioriation of the bronze thru hull portion of the original shaft log. Is there any non-destructive way to determine the soundness of the bronze thru hull components? On my 28.5, none of the thru hulls, nor the strut are bonded or grounded, though, presumably, the shaft , prop, zincs and engine are all in contact with each other. Any sage observations from the knowledgable electrical engineers in the group?
Good Zincs v. Silent Menace
No doubt there's potential for heavy electrolysis damage due to a lot of boats in close proximity, but if this is the only part that was damaged -- and finding it can be scary -- then were other parts protected by zincs attached to them directly or what? You know, "reverse" electrolysis from a DC "leak" inside the boat often times goes right down the shaft and since this appears to be something of an interior part, having the DC system inside the boat checked might not be a bad idea. Recently, I had to replace both the shaft strut and shaft on my 78h30 -- Shut up, Steve! That's a whole 'nuther story!! -- and had all the parts checked and replaced if they showed any sign of normal wear or electrolysis. In my case, everything turned out ok, but every year I have the boat checked for DC leaks. And, I've also go enough of those fish-shaped sacrificials hanging off my boat that is looks like I got a trotline going! Just some thoughts about how we've embraced and conquered the "silent menace" down my way.
No doubt there's potential for heavy electrolysis damage due to a lot of boats in close proximity, but if this is the only part that was damaged -- and finding it can be scary -- then were other parts protected by zincs attached to them directly or what? You know, "reverse" electrolysis from a DC "leak" inside the boat often times goes right down the shaft and since this appears to be something of an interior part, having the DC system inside the boat checked might not be a bad idea. Recently, I had to replace both the shaft strut and shaft on my 78h30 -- Shut up, Steve! That's a whole 'nuther story!! -- and had all the parts checked and replaced if they showed any sign of normal wear or electrolysis. In my case, everything turned out ok, but every year I have the boat checked for DC leaks. And, I've also go enough of those fish-shaped sacrificials hanging off my boat that is looks like I got a trotline going! Just some thoughts about how we've embraced and conquered the "silent menace" down my way.
Sounds like the shaft log
Hmm... sounds like the part I was referring to would be the shaft log. It's a brass tube bolted on from the outside that leads inside to the packing area. The prop shaft passes through it, and I believe the cutless bearing rests inside it. My mechanic constructed a new one from stainless. You've got me wondering about DC leaks now. I've had the boat two years now, but prior to that it spent a lot of time in the marina. Some three years were spent at a Cuban marina, where the electrical system is horrific by our standards. Since I've been on the hook for the past two years I'm wondering if a DC leak might be occuring. I use a portable generator to charge the batteries or run the engine. Hard to tell when this occured, could be years of activity. How does one check for a DC leak?
Hmm... sounds like the part I was referring to would be the shaft log. It's a brass tube bolted on from the outside that leads inside to the packing area. The prop shaft passes through it, and I believe the cutless bearing rests inside it. My mechanic constructed a new one from stainless. You've got me wondering about DC leaks now. I've had the boat two years now, but prior to that it spent a lot of time in the marina. Some three years were spent at a Cuban marina, where the electrical system is horrific by our standards. Since I've been on the hook for the past two years I'm wondering if a DC leak might be occuring. I use a portable generator to charge the batteries or run the engine. Hard to tell when this occured, could be years of activity. How does one check for a DC leak?
Also important: install a galvanic isolator
If your boat is equipped with shore power, you have established a common ground (via the green wire) with the dock and nearby boats -- which MAY mean that your boat's submerged metal parts have become part of a gigantic battery. The resulting galvanic corrosion can be very destructive, as this thread illustrates. Happily, there is a simple cure: install a galvanic isolator. The isolator blocks dangerous galvanic currents (low-voltage DC, typically less than 1.2 volts) but allows high-voltage AC to pass. Galvanic isolators (about $200-$250) use diodes to block the DC currents. NOTE: ABYC has apparently specified that galvanic isolators should include self-monitoring LEDs (effective July 2002). Two units that provide these features are the Guest 2433P (30 amp) and 2450P (50 amp). Cheaper units lack the ABYC-mandated integrated monitoring features. There are three rationales for going with the more expensive, ABYC-conforming units: (1) If you sell your boat and get an ABYC-happy surveyor, you may find yourself upgrading the unit in order to complete the deal; (2) non-conforming units could be installed in a way that is dangerous. You can test the installation, but it's tricky, I'm told; (3) Galvanic isolators perform a crucial role in the boat's electrical system, and the more expensive units have heat protection and backup circuits. As Peter Kennedy says, it's only prudent to use the best available unit (http://www.pkys.com/galvanic_isolators.htm. (I highly recommend Mr. Kennedy's Web site -- http://www.pkys.com for information on marine electrical systems and related products.) Also note: The West Marine catalog and Guest's Web site catalog states that the cheaper Guest units conform to ABYC standards, but this doesn't appear to be the case -- they don't have self-monitoring capabilities -- perhaps someone more informed than me could comment??? Succinct background article: http://www.adverc.co.uk/products/protection/galvanic.asp Typical installation schematic: http://www.dairyland.com/schematic.pdf Test prodecure for units lacking self-monitoring capabilities: http://www.pkys.com/Folder1/Galvanic%20Isolator%20test%20procedure.htm Disclaimer: I'm not an expert in this area! The above is what I've worked through in figuring out which galvanic isolater to purchase. Unless you are sure you know what you are doing, it's really a good idea to have an ABYC certified electrician install and test a galvanic isolator.
If your boat is equipped with shore power, you have established a common ground (via the green wire) with the dock and nearby boats -- which MAY mean that your boat's submerged metal parts have become part of a gigantic battery. The resulting galvanic corrosion can be very destructive, as this thread illustrates. Happily, there is a simple cure: install a galvanic isolator. The isolator blocks dangerous galvanic currents (low-voltage DC, typically less than 1.2 volts) but allows high-voltage AC to pass. Galvanic isolators (about $200-$250) use diodes to block the DC currents. NOTE: ABYC has apparently specified that galvanic isolators should include self-monitoring LEDs (effective July 2002). Two units that provide these features are the Guest 2433P (30 amp) and 2450P (50 amp). Cheaper units lack the ABYC-mandated integrated monitoring features. There are three rationales for going with the more expensive, ABYC-conforming units: (1) If you sell your boat and get an ABYC-happy surveyor, you may find yourself upgrading the unit in order to complete the deal; (2) non-conforming units could be installed in a way that is dangerous. You can test the installation, but it's tricky, I'm told; (3) Galvanic isolators perform a crucial role in the boat's electrical system, and the more expensive units have heat protection and backup circuits. As Peter Kennedy says, it's only prudent to use the best available unit (http://www.pkys.com/galvanic_isolators.htm. (I highly recommend Mr. Kennedy's Web site -- http://www.pkys.com for information on marine electrical systems and related products.) Also note: The West Marine catalog and Guest's Web site catalog states that the cheaper Guest units conform to ABYC standards, but this doesn't appear to be the case -- they don't have self-monitoring capabilities -- perhaps someone more informed than me could comment??? Succinct background article: http://www.adverc.co.uk/products/protection/galvanic.asp Typical installation schematic: http://www.dairyland.com/schematic.pdf Test prodecure for units lacking self-monitoring capabilities: http://www.pkys.com/Folder1/Galvanic%20Isolator%20test%20procedure.htm Disclaimer: I'm not an expert in this area! The above is what I've worked through in figuring out which galvanic isolater to purchase. Unless you are sure you know what you are doing, it's really a good idea to have an ABYC certified electrician install and test a galvanic isolator.
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