A friend of mine gave me a "Zinc Saver" which is an electronic component that connects between the boat's AC ground and bonding system. It monitors and reduces the potential current to the boat's ground, thereby reducing (eliminating?) the electrolsis process. If this system works right, it should reduce the deterioration rate of the zinc collars on my prop shaft. The plus would be a smoother running shaft. However, another friend of mine has heard of zinc saver malfunctions and the result was rapid electrolsis and severe damage to the underwater metals (prop, propshaft. rudder post, etc). Have any of our Hunterowners out there in sailing-cyberland installed a zinc saver and if so has it performed to your expectations? Appreciate any response! JoeO
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Galvanic Isolators
I'm no electrical engineer, but work and sail with some and the "zinc savers" or galvanic isolators make a lot of sense when someone explains the problem with keeping your shore power cable attached. The galvanic isolator blocks the current from entering through your ground line, which is a major source of galvanic action, but allows the AC ground to carry full amperages. I put one on my boat and am surprised they are not more common. Apparently there were some problems with early models, but those have been taken care of and the isolators meet ABYC requirements. West Marine sells them.
I'm no electrical engineer, but work and sail with some and the "zinc savers" or galvanic isolators make a lot of sense when someone explains the problem with keeping your shore power cable attached. The galvanic isolator blocks the current from entering through your ground line, which is a major source of galvanic action, but allows the AC ground to carry full amperages. I put one on my boat and am surprised they are not more common. Apparently there were some problems with early models, but those have been taken care of and the isolators meet ABYC requirements. West Marine sells them.
I'm a bit confused...
But then, my expertise is in plumbing...I know just enough about electrical systems to be dangerous, and with that in mind, something doesn't seem to be adding up: We put zincs on our boats to protect them from electrolytic corrosion. Now someone is asking about a "zinc saver" device to protect the zinc that's protecting the boat. (What's next--a device to protect the "zinc saver?") If the "zinc saver" protects the zinc, isn't it also doing the zinc's job? Why would you need both?
But then, my expertise is in plumbing...I know just enough about electrical systems to be dangerous, and with that in mind, something doesn't seem to be adding up: We put zincs on our boats to protect them from electrolytic corrosion. Now someone is asking about a "zinc saver" device to protect the zinc that's protecting the boat. (What's next--a device to protect the "zinc saver?") If the "zinc saver" protects the zinc, isn't it also doing the zinc's job? Why would you need both?
Stop the Current vs. Sacrificial Zinc
Peggy, I'm not expert, but Calder explains (Boatowner's Mechanical and Electrical Manual) that the galvanic action that disolves the zincs, occurs because of a current flowing between the metal on the boat and the water. This can happen because shore power frequently uses a common that is directly or indirectly connected to ground. So some current from the common on board your boat, conducts through the metal, say propellor shaft, into the water, back to the ground. The propellor and shaft would disolve, going with the flow of electrons, but the current would rather flow through through the zinc, than bronze, so the zinc disolves, not your propellor. Add a galvanic isolator: The isolation devices (essentially isolation tranformers) isolate the shore power from that on the boat, because there is no direct connection between the ac power on the shore, and that on the boat. The shore power goest to a primary coil in the transformer. The boats power source is the secondary side of the transformer. Any onboard current leakage goes back through the transformer, and not out your propellor into the water. The boats ground is not connected to the shore ground wire, so there is no path for galvanic currents. So this does make sense, sort of...
Peggy, I'm not expert, but Calder explains (Boatowner's Mechanical and Electrical Manual) that the galvanic action that disolves the zincs, occurs because of a current flowing between the metal on the boat and the water. This can happen because shore power frequently uses a common that is directly or indirectly connected to ground. So some current from the common on board your boat, conducts through the metal, say propellor shaft, into the water, back to the ground. The propellor and shaft would disolve, going with the flow of electrons, but the current would rather flow through through the zinc, than bronze, so the zinc disolves, not your propellor. Add a galvanic isolator: The isolation devices (essentially isolation tranformers) isolate the shore power from that on the boat, because there is no direct connection between the ac power on the shore, and that on the boat. The shore power goest to a primary coil in the transformer. The boats power source is the secondary side of the transformer. Any onboard current leakage goes back through the transformer, and not out your propellor into the water. The boats ground is not connected to the shore ground wire, so there is no path for galvanic currents. So this does make sense, sort of...
Peggy... there is a great article in the
September issue of crusing world magazine. It's on page 90 and explains the whole deal and discusses 5 brands of galvanic isolators.. Dick McKee S/V Constellation
September issue of crusing world magazine. It's on page 90 and explains the whole deal and discusses 5 brands of galvanic isolators.. Dick McKee S/V Constellation
My Hunter 42 Has a zinc saver
I was working behind my electrical panel just tonight and noticed that I have installed (evidently by Hunter) a ZINC SAVER too. If its good enough to be installed by Hunter, it good enough for ...
I was working behind my electrical panel just tonight and noticed that I have installed (evidently by Hunter) a ZINC SAVER too. If its good enough to be installed by Hunter, it good enough for ...
I guess my question is:
I understand what the "zinc saver does"...But if the zinc protects the boat, and the "zinc saver" protects the zinc...why do you need the zinc? Wouldn't the isolator do the entire job?
I understand what the "zinc saver does"...But if the zinc protects the boat, and the "zinc saver" protects the zinc...why do you need the zinc? Wouldn't the isolator do the entire job?
More than one source of current
I understand that there is more than one source for the stray current that causes electrolysis. The isolator stops it from coming over the common ground, but if a boat near you in a marina has a problem, you can get it through the water as well. Zincs are probably enough most of the time, but I have seen enough bad electrolysis (on other boats thankfully) that the theory made sense and the isolator seemed like good protection for me.
I understand that there is more than one source for the stray current that causes electrolysis. The isolator stops it from coming over the common ground, but if a boat near you in a marina has a problem, you can get it through the water as well. Zincs are probably enough most of the time, but I have seen enough bad electrolysis (on other boats thankfully) that the theory made sense and the isolator seemed like good protection for me.
not just AC
On the factory-installed zinc saver on my 410, the DC and AC grounds are connected at the zinc saver post...... Peggy, if you have a zinc saver you still need sacrificial zincs, it's just that they won't degrade as quickly. On my boat, in a very "hot" marina, (there's a 110' classic steel yacht on the end tie close to me) the zinc saver allows me to go three months before changing the shaft zinc. Without it, there's no way I'd be able to go more than two months.
On the factory-installed zinc saver on my 410, the DC and AC grounds are connected at the zinc saver post...... Peggy, if you have a zinc saver you still need sacrificial zincs, it's just that they won't degrade as quickly. On my boat, in a very "hot" marina, (there's a 110' classic steel yacht on the end tie close to me) the zinc saver allows me to go three months before changing the shaft zinc. Without it, there's no way I'd be able to go more than two months.
Don't depend on the Zinc Saaver to protect your boat. There is one on my P42 and it doens't get the job done. I use prop zincs and when pluged in for a time I also use an overboard zinc. A lot depends on your boat, it's location and other surrounding boats, the salinity of the water is also a factor. I saw a 35 Hunter with the strut completely gone from corrosion.
A Scary Thought ...................
After reading through a few of these replies, it finally dawned on my fuzzy little brain that the bronze shaft strut is NOT electrically connected to the SS shaft which carries three zincs nor to the overboard zinc (we have extreme corrosion here). Now I have something else to lose sleep over at night or is there some other form of salvation which I am not seeing. Regards, Island Hunter
After reading through a few of these replies, it finally dawned on my fuzzy little brain that the bronze shaft strut is NOT electrically connected to the SS shaft which carries three zincs nor to the overboard zinc (we have extreme corrosion here). Now I have something else to lose sleep over at night or is there some other form of salvation which I am not seeing. Regards, Island Hunter
Sleep Well Ralph!
In order for electrolysis to take place, there has to be an electrical connection between two metals, both in contact with the water (in this case). The shaft, connects to the engine, and then to the ground on the boat. So stray currents can flow through the engine, to the shaft, and then into the water, taking some metal with them! But, as to your bronze shaft strut, you are right, the cutlass bearing will insulate it so it is not connected electrically to the stainless steel shaft. But it also in not grounded to the rest of the system. That is a good thing, since no current will try to escape from it into the surrounding water. So it should not be subjected to electrolysis. This is a little easier to understand when you think of how a battery works. The plates sitting in the electrolytic solution really don't deteriorate until a wire, or other devices, connect the two terminals. It is only then that the electrons from one piece of metal can flow to the other. They need that wire to get back to where they started, and do it all again! Of course any metal will slowly corrode, but your strut should not present a problem. Now, if your cutlass bearing is worn out, and makes a metal connection between the stainless steel shaft and the bronze strut...
In order for electrolysis to take place, there has to be an electrical connection between two metals, both in contact with the water (in this case). The shaft, connects to the engine, and then to the ground on the boat. So stray currents can flow through the engine, to the shaft, and then into the water, taking some metal with them! But, as to your bronze shaft strut, you are right, the cutlass bearing will insulate it so it is not connected electrically to the stainless steel shaft. But it also in not grounded to the rest of the system. That is a good thing, since no current will try to escape from it into the surrounding water. So it should not be subjected to electrolysis. This is a little easier to understand when you think of how a battery works. The plates sitting in the electrolytic solution really don't deteriorate until a wire, or other devices, connect the two terminals. It is only then that the electrons from one piece of metal can flow to the other. They need that wire to get back to where they started, and do it all again! Of course any metal will slowly corrode, but your strut should not present a problem. Now, if your cutlass bearing is worn out, and makes a metal connection between the stainless steel shaft and the bronze strut...
Cruising World Article...
Dick, thanks for the tip on the Sept. Cruising World article. They make a good point that one should monitor the performance of the isolator. I checked out Promariner's website and they sell monitoring panels that mate up with their galvanic isolators. I think I'll also pick up the authors book on powerboat electrical systems. thanks again! JoeO
Dick, thanks for the tip on the Sept. Cruising World article. They make a good point that one should monitor the performance of the isolator. I checked out Promariner's website and they sell monitoring panels that mate up with their galvanic isolators. I think I'll also pick up the authors book on powerboat electrical systems. thanks again! JoeO
But Ralph,
despite Ron's good news, it's a good idea to have a clamshell zinc installed on the strut. Unfortunately, this means drilling a hole through the strut, an operation best done when the boat is hauled. Sleep well, as Ron advises, but if you do this during your next haulout, you may sleep even better. (My clamshell, by the way, doesn't deteriorate nearly as fast as the shaft zincs. Most people can probably go a full year with each zinc put on the strut.)
despite Ron's good news, it's a good idea to have a clamshell zinc installed on the strut. Unfortunately, this means drilling a hole through the strut, an operation best done when the boat is hauled. Sleep well, as Ron advises, but if you do this during your next haulout, you may sleep even better. (My clamshell, by the way, doesn't deteriorate nearly as fast as the shaft zincs. Most people can probably go a full year with each zinc put on the strut.)
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