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post #1 of 32 Old 11-10-2016 Thread Starter
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Sad looking zinc's

These are the zinc's at the end of the school year on one of the school boats.
Even with the bad picture I think you can see they are mostly gone.

Does this mean that damage was done since they are so badly eaten up.

Should we put on three next year?

The other boat had zincs in much better condition.

What else should we look for or fix?
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post #2 of 32 Old 11-10-2016
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Re: Sad looking zinc's

Get yourself a corrosion reference electrode and learn how to use it.

Corrosion Reference Electrode Product Specifications


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post #3 of 32 Old 11-11-2016
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Re: Sad looking zinc's

im going to have to look into that.
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Re: Sad looking zinc's

Quote:
Originally Posted by davidpm View Post
These are the zinc's at the end of the school year on one of the school boats.
Even with the bad picture I think you can see they are mostly gone.

Does this mean that damage was done since they are so badly eaten up.

Should we put on three next year?

The other boat had zincs in much better condition.

What else should we look for or fix?
Adding more zinc's isn't the solution to your problem and may be contra-productive, particularly if any are situated near mid-way between the shaft strut and the packing gland. As the zinc's erode, the irregular wasting creates an imbalance of the weight distribution about the longitudinal axis of the shaft. As the shaft rotates, the imbalance causes the shaft to "whip" or wobble which leads to rapid deterioration of the cutlass bearing and your packing gland packing material. You should have a single zinc, situated about 6"-8" from the shaft strut, that is replaced when more than 25%-30% of the zinc has wasted. Any diver can change a zinc in a few minutes without difficulty (and take a few minutes to give your prop and running gear a scrub to clear it of "growies"). While zinc's are not inexpensive, one relatively less costly source is "Boatzincs.com" where a 30mm shaft "olive" was only about $9.00 USD the last time I checked.

FWIW...
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post #5 of 32 Old 11-11-2016
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Re: Sad looking zinc's

In addition to the good posting by svHyLyte, also consider to buy 'quality' anodes rather than 'bargains', as the better metallurgical composition of a 'quality' zinc, etc. anode will usually far outlast 'cheap bargain basement junk'.
Look for anodes composed of MIL-SPEC zinc alloy .... as such won't usually come apart in 'chunks' as they are used up. The higher quality anodes will usually also have internal reinforcements to help avoid such 'chunking' and premature falling apart.

;-)
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post #6 of 32 Old 11-11-2016
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Re: Sad looking zinc's

Mine looked slightly worse. I'm going to have to look into that.

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Re: Sad looking zinc's

teach the fine art of underwater maintenance--- zinc replacement 101 a
monthly hull cleanings and inspections are helpful with replacement as needed.
one of the best preparatory classes ever.
must know how to maintain and repair ones equipment.
there are threads on overzincing, which can cause damage as opposed to aiding in prevention.


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post #8 of 32 Old 11-11-2016
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Re: Sad looking zinc's

Changing to aluminum anodes will help here: Shaft Aluminum Anodes - Standard (X-1AL thru X-17AL) . However, if you have a bonding or galvanic problem, nothing helps as much as solving that.

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Re: Sad looking zinc's

Given that one boat is ok and the other shows quite a bit of anode wasteage, I'd be looking for a little bit of stray current corrosion, bilge pump floats are a very common cause. is there any other corrosion evident ? Is the propeller turning slightly pink along the blade tips ? is the shaft pitted (even minutely) ?

I'd suggest against the use of aluminum anodes in salt water as they are more galvanically active and will disappear even faster than zinc.
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post #10 of 32 Old 11-11-2016
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Re: Sad looking zinc's

Quote:
Originally Posted by zeehag View Post
teach the fine art of underwater maintenance--- zinc replacement 101 a
monthly hull cleanings and inspections are helpful with replacement as needed.
one of the best preparatory classes ever.
must know how to maintain and repair ones equipment.
there are threads on overzincing, which can cause damage as opposed to aiding in prevention.
Those of us who are forced to haul before the snow flies don't need so much hull cleaning. I was in the water for about 6 month and came out shy a couple of zinc but with just a coat of slime that easily washed off.

I will have to look into what exactly over-zincing is all about.
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