I have a new 2000 Hunter 340. It did not come with zinc's. How many should I use on the propeller shaft? Thanks for the help.
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hp
zinc's
I always use two of the shaft zinc's.They are cheap enough and can never have to much protection but at least use one. Your boat has a 1 inxh shaft and mount them forward of the shaft strut. Do not paint them!
I always use two of the shaft zinc's.They are cheap enough and can never have to much protection but at least use one. Your boat has a 1 inxh shaft and mount them forward of the shaft strut. Do not paint them!
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Steve O.
shaft zincs
Don't mount them too close to the cutless bearing or they will cut off the water flow to the bearing which is necessary for cooling the bearing when motoring. Stay about 4-6" forward of the bearing.
Don't mount them too close to the cutless bearing or they will cut off the water flow to the bearing which is necessary for cooling the bearing when motoring. Stay about 4-6" forward of the bearing.
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R. Young
Mounting the zincs
I use 2 zincs - in the past, using only one on my Hunter 37 - It was very used (corroded) by the end of the season. Also take care in how you mount it. At the end of the season, previously it was no longer there. The yard people at the marina told me to tighten the screws as much as possible. Then give it a few wacks with a hammer and you should be able to retighten. Clean the shaft with light sandpaper or emory till shiny, mount the zincs. Do not paint over the zinc - ok to paint over the other exposed shaft area.
I use 2 zincs - in the past, using only one on my Hunter 37 - It was very used (corroded) by the end of the season. Also take care in how you mount it. At the end of the season, previously it was no longer there. The yard people at the marina told me to tighten the screws as much as possible. Then give it a few wacks with a hammer and you should be able to retighten. Clean the shaft with light sandpaper or emory till shiny, mount the zincs. Do not paint over the zinc - ok to paint over the other exposed shaft area.
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Bryan C.
You can have too many zincs
So don't get the idea of slapping 6 of them on for permanent protection. If you are in a place where you or somebody can dive down to check the zinc when the boat is in the water, I'd put one on first and then check it in about 3 months. If diving in the water is not practical, I'd put two on and see how they look after the next haul out. I carry 2, but if I carry one I need to replace it about every 3 months. Either my marina or boat has a stray electrical leak.
So don't get the idea of slapping 6 of them on for permanent protection. If you are in a place where you or somebody can dive down to check the zinc when the boat is in the water, I'd put one on first and then check it in about 3 months. If diving in the water is not practical, I'd put two on and see how they look after the next haul out. I carry 2, but if I carry one I need to replace it about every 3 months. Either my marina or boat has a stray electrical leak.
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Gerry Libertelli
Yep! Three is too many
I just got done putting S.V. Persistence (1999 h380) in the water. When we got to the topic of Zincs, I said "lets slap three on there and maybe we wont have to worry about corrosion so early". My yard said that the max they would recommend is two. Three causes some sort of instability in the shaft. Anyone know why? They dribbled out some nonsense, but I was much more interested in saling than listening. Gerry
I just got done putting S.V. Persistence (1999 h380) in the water. When we got to the topic of Zincs, I said "lets slap three on there and maybe we wont have to worry about corrosion so early". My yard said that the max they would recommend is two. Three causes some sort of instability in the shaft. Anyone know why? They dribbled out some nonsense, but I was much more interested in saling than listening. Gerry
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R.W. Landau
Yes, you can over zinc
Zincs in the salt water become anodes of a battery. The more zinc, the bigger the battery. The idea is to create an flow of electrons from the zinc (being the anode of the battery) and not from the bronze or stainless (keeping them cathodes). If the protection is to great, alkalinity will increase. Alkalinity is corrosive to aluminum and steel. Stainless does have impurities and over protection will bring them out. I would stick with two and examine results. r.w.landau
Zincs in the salt water become anodes of a battery. The more zinc, the bigger the battery. The idea is to create an flow of electrons from the zinc (being the anode of the battery) and not from the bronze or stainless (keeping them cathodes). If the protection is to great, alkalinity will increase. Alkalinity is corrosive to aluminum and steel. Stainless does have impurities and over protection will bring them out. I would stick with two and examine results. r.w.landau
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Carl Reitz
Sleep well with 3
Our 1987 h40 had three zincs on the shaft when we bought it. I put 3 new ones on every year. There is always a good deal left after eight months in the slip. While we could probably save $7 and cut back to two, we view the third as good insurance. As for instability, I've never noticed any. Suspect the added weight would aggrevate an out-of-line installation. The answer then would be fix the installation by properly alligning the prop and engine: not use less zinc. Carl Reitz S/v Windrose
Our 1987 h40 had three zincs on the shaft when we bought it. I put 3 new ones on every year. There is always a good deal left after eight months in the slip. While we could probably save $7 and cut back to two, we view the third as good insurance. As for instability, I've never noticed any. Suspect the added weight would aggrevate an out-of-line installation. The answer then would be fix the installation by properly alligning the prop and engine: not use less zinc. Carl Reitz S/v Windrose
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David
Zincs
The best shaft zinc I have found is a Godfrey. It has a thick bronze ring for better contact aand is more difficult for the shaft to throw. It is expensive. Don't worry about too many zincs. You can't over zinc unless you have a wood hull where fastenings come into play.
The best shaft zinc I have found is a Godfrey. It has a thick bronze ring for better contact aand is more difficult for the shaft to throw. It is expensive. Don't worry about too many zincs. You can't over zinc unless you have a wood hull where fastenings come into play.
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R.W.Landau
David , I beg to differ.
David, I am sorry that I did not back up my last statement. In Nigel Calders book "Boatowner's Mech and elec" Page 146,(Impressed currents). Combine that info with the info on page 134, "dezincification and crevice corrosion" his statement that even "pure" metals have impurities. I would be carefull not to over zinc the boat. Though the damage may be minor, I would use a larger zinc, not more of them. Again, the surface area of the zinc determines the amount of protection and the weight determines the duration of the protection. If you are worried about how long they will last, use a larger zinc. r.w.landau
David, I am sorry that I did not back up my last statement. In Nigel Calders book "Boatowner's Mech and elec" Page 146,(Impressed currents). Combine that info with the info on page 134, "dezincification and crevice corrosion" his statement that even "pure" metals have impurities. I would be carefull not to over zinc the boat. Though the damage may be minor, I would use a larger zinc, not more of them. Again, the surface area of the zinc determines the amount of protection and the weight determines the duration of the protection. If you are worried about how long they will last, use a larger zinc. r.w.landau
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David
R. W.
UNDERSTANDING MARINE CORROSION prepared for and presented by The American Boat and Yacht Council on page 59 provides information on overprotection and underprotection, "Overprotection wastes money (on excess zinc or impressed protective current), it causes zincs and impressed-current anodes to waste away prematurely, and for metals in contact with wood, it increases the production of hydroxyl ions which can damage wood." If you e-mail me we can continue a discussion of cathodic protection.
UNDERSTANDING MARINE CORROSION prepared for and presented by The American Boat and Yacht Council on page 59 provides information on overprotection and underprotection, "Overprotection wastes money (on excess zinc or impressed protective current), it causes zincs and impressed-current anodes to waste away prematurely, and for metals in contact with wood, it increases the production of hydroxyl ions which can damage wood." If you e-mail me we can continue a discussion of cathodic protection.
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