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Old 18-09-2017, 09:17   #1
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Zincs and bottom

Hi,

I have two questions, I'd appreciate some feedback/advice:

1. How often do you typically replace the zincs? Or, better phrased perhaps, how do you know that the zincs need to be replaced without taking the boat out of the water or sending a diver (or yourself) to check them?

2. How often do you typically clean the bottom (just cleaning)? We would not put the boat on the hard, we would hire a diver at this time.

Thank you!
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Old 18-09-2017, 18:47   #2
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Re: Zincs and bottom

Mine is probably not the typical answer, but it'll be one point along the bell curve when you get the others' responses. I'm also a diver and can check/change the zincs whenever I need. For #1, when I first bought the boat, I used to have to change the zincs every 2 months because of stray current. Since a complete rewiring was done 2 years ago, I have lost count and it seems to be more on the order of 6 months. I have two zincs on my prop shaft, so I replace one when it is about half way pitted and degraded, and before the screws are exposed. I don't think there's any way to tell (short of sending a diver or camera down) whether a zinc needs replacing without looking at it.

For #2, I clean my boat about every 6 weeks before a big race. I race more often than that, but the bottom stays clean enough. I also took all the ablative paint off in my last haulout (April 2016) and put on hard paint, figuring that it would better hold up to my more aggressive approach to bottom cleaning. I also only clean the bottom with a shammy cloth -- no abrasives or scraping allowed (or needed)!!

No matter what kind of answers you get here, your diver can also advise you about what is seen and how often the zincs need to be replaced. Under normal conditions, I would think it could be done every 4-6 months. You'll get much better performance out of the boat with a clean bottom, too!
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Old 19-09-2017, 09:42   #3
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Re: Zincs and bottom

Hi Gamayun,
Thank you for the reply.
Actually, sending a camera down to check seems like a very good idea to me, especially here in the PNW. I'll try with my GoPro.
Thanks,
Fabio
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Old 19-09-2017, 10:02   #4
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Re: Zincs and bottom

Typically 1-1.5 years on zincs and they are pretty gone. In a "hot" marina, or a "hot" boat, they can go very fast though. Anyone cleaning your bottom can tell if they need replaced. How often you clean is about how often you use the boat and the growth situation where you moor the boat. They can get ugly in 3 months with algae/grass growing 6" long in some locales, or maybe a year in other places.
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Old 19-09-2017, 10:13   #5
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Re: Zincs and bottom

The answer to both of your questions are high dependent on the locale you keep your boat in or the waters you travel through. Zincs will get eaten at different rates depending on the composition of the water you're in as well as other factors, such as localized currents in a marina.

Boat bottoms will foul at different rates again depending on the water (brackish, salt, cool, warm, nutrient rich etc.) as well as your type of bottom paint and how often the boat is moving.

I check my zincs every 6 months, at least. If I'm in water where I can't see them or is too cold to swim, I have a cheap Go Pro clone camera that I snap on the end of a boat hook and poke down to take a look.
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Old 19-09-2017, 10:29   #6
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Re: Zincs and bottom

When in the Caribbean, we need to clean the bottom monthly. When home in Florida, every 3 months depending on use. When up north in New England, once a year. In other words, it depends...
Same with zincs.
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Old 20-09-2017, 14:06   #7
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Re: Zincs and bottom

My boat is in Campbell River on Discovery Passage - lots of water flow and water flowing in may be cooler than your area. I change the zincs annually and haul the boat for bottom painting every 3 years. I have the bottom cleaned by a diver in between haulouts along with the annual zinc inspection. I cruise and don't race so may be less concerned about keeping the bottom really clean. I did check the zincs more often in the early days at the marina to establish how quickly they were being consumed, and to satisfy myself that annually was ok. I have 2 on the prop shaft.
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Old 28-09-2017, 21:37   #8
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Re: Zincs and bottom

Galvanic isolators are cheap and just need connecting to your ground wire. Drops the rate of zinc consumption by over 3/4ths in a hot marina in my experience.
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Old 29-09-2017, 08:58   #9
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Re: Zincs and bottom

Here's what I use to do inspections without getting into the water. $250:



https://shop.vexilar.com/en/fish-pho...complete-fp100
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