Anode installation - best practices

[fstbttms]

Man- you guys are waaay overthinking this thing.

 

[JamesG161]

Keep in mind that one half of the PSS is a carbon block directly in contact with a SS rotor which is directly in contact with the prop shaft. I have noted increases in zinc erosion speed on almost every boat I have installed a PSS on, including all of my own boats I installed a PSS on.. Is this bad? Not necessarily, but the zincs just won't last as long and you should not let them entirely waste. I much prefer to see a PSS used with an AQ-19 or AQ-22 shafting material rather than bronze (really brass) or lower grades of SS. Everytime I install graphite packing or a PSS i let the owner know to check the anodes more frequently until they get a sense of anode life.

Although I have learned not to disagree with Maine Sail (the hard wayI am yellow), in this case I will temper my response.

The Zinc protects the Carbon seal face (not pure Graphite) of the PSS TOO!!

The rate of corrosion of your Zinc (no stray currents) is directly related to the surface area of the metal exposed ( or Galvanic material down the list from zinc) to protect, in addition to what Maine Sail said about the Maximum voltage difference.

IMHO, changes in water salinity and temperature would have more effect on zinc loss rate than the very very small surface of the PSS carbon, but it would have an effect.

I would NOT rush out and change my PSS back to packing, is my point.
Jim...

PS: I am ducking for cover under my Nav table now.

 

[woodster]

Man- you guys are waaay overthinking this thing.

Not really when think about replacing prop,strut,shaft,pas seal or stuffing box all at the same time ...ask me how I know....I have done this...two zincs are at worst $30.00 compaired to $2500.00 for the other stuff at minimum .....

 

[fstbttms]

Not really when think about replacing prop,strut,shaft,pas seal or stuffing box all at the same time ...ask me how I know....I have done this...two zincs are at worst $30.00 compaired to $2500.00 for the other stuff at minimum .....

I'm referring to the worry about balance, offsetting the mounting screws etc.- totally unnecessary IMHO.

 

[JamesG161]

Interestingly, the electrical prints show only the yellow wire dc return ground bus connected to an engine bolt. The green/yellow wire bonded components (keel, chainplates, mast, compression post, forestay, arch, diesel filer neck) apparently do not tie to an engine bolt that I can find yet.

My Hunter 430 is the same. I have the Ag/AgCl electrode and used it to enlighten me and clear up the wiring.
http://www.boatzincs.com/corrosion-reference-electrode-specs.html

I have been slowly reading many of the ABYC electrical standards linked by Maine Sail and some extras ones.
On my boat, the only spot for the DC (and I believe AC GFIC green wire ground) ground is the negative terminal of the engine starter battery (not the engine bolts). The engine starter ground to Negative Battery terminal wire should be ( from memory) less than 1 ohm resistance. Why? So very very little DC amps flows through the engine, shaft, prop, et. al. during the start.

Using the Ag/AgCl reference probe and the chart above, I checked ....
Engine, shaft, PSS seal , propeller, and shaft zinc.... -983mVolts... YESSSSS!!!! all protected by the shaft zinc in the water.
Then I moved to the Bond System check....
OMG -400mVolts!!!! My standing rigging, rudder and keel bolts must be ready to fall apart.
Heart attack time?

Nope. My Lead/Antimony keel. Which is no biggie if and only if the Bond system is never ever used for a DC current path (this includes stray DC current from other nearby badly wired boats).

I now use that Ag/AgCl probe each month to make sure of other boats. Mine was wired right.
If you do the Electrical Survey provided with the probe, you will find if you boat is wired wrong and what is causing it.
Jim...

 

[Bill Roosa]

Presumably the zinc wasting is happening at the slip. Sooooo why not grab one of those big zinc 'fish" or a bunch of random zincs and wire them together. run a wire from them to the engine block ground or where ever you are trying to protect some metal parts and then drop it over the side of the boat when at the slip. Should help prevent the hard to replace zinc wasting with easy to replace zinc wasting.
FWIW

 

[Dan_Y]

Presumably the zinc wasting is happening at the slip. Sooooo why not grab one of those big zinc 'fish" or a bunch of random zincs and wire them together. run a wire from them to the engine block ground or where ever you are trying to protect some metal parts and then drop it over the side of the boat when at the slip. Should help prevent the hard to replace zinc wasting with easy to replace zinc wasting.
FWIW

Bill - Good advice...That's exactly what I did to buy time until I can figure out what might be causing accelerated wasting of th zincs. Charles had suggested this as well.

 

[JamesG161]

Presumably the zinc wasting is happening at the slip. Sooooo why not grab one of those big zinc 'fish" or a bunch of random zincs and wire them together. run a wire from them to the engine block ground or where ever you are trying to protect some metal parts and then drop it over the side of the boat when at the slip. Should help prevent the hard to replace zinc wasting with easy to replace zinc wasting.

A drop zinc will only spread the loss from you normal zincs and NOT stop it. I use the zinc fish in when in a transient Marina to protect from possible stray currents.
If you want to stop the wasting of your hard to install zincs, use this drop anode...
http://www.boatzincs.com/hanging_anode_magnesium.html
Normally magnesium anodes are used in freshwater, only because freshwater is lower electrical conductivity. They work in saltwater too.
Magnesium is more expensive per pound than zinc, but not if you have to dive the boat to change zinc.

Look at Maine Sail's galvanic chart, post#20. Magnesium is first on that chart, therefore will stop Zinc waste if the Magnesium is connected electrically to the same metal as your expensive zinc.
Jim...

PS: Remember to disconnect your drop anode from your shaft, before starting your engine.

 

[fstbttms]

You should not want to stop zinc depletion. Anodes sacrifice themselves in place of something more important, like your prop or shaft. This is what they are supposed to do (hence the term, "sacrificial anodes.") If you are experiencing rapid anode depletion, it is indicative of an electrical problem that needs rectification, not a band-aide like a fish anode.

 

[Dan_Y]

"...If you are experiencing rapid anode depletion, it is indicative of an electrical problem that needs rectification, not a band-aide like a fish anode."

Again I agree, but I need the band aid to buy time to properly troubleshoot and fix. I have narrowed my electrical problems to a potential electrical leak in the bilge wiring, a 6 mA current flowing from each of two batteries back to the charger when the charger power is off and all other DC circuits are opened (24hour loads off as well) and a vhf receiver that is potentially leaking DC into the mast when powered on. The latter is probably not the issue given the small amount of time it's on, but is a problem though. Will report results when done. I'm getting great, helpful suggestions from the forum.

 

[GonzoF1]

I like to see it two finger lengths from the strut. This limits unbalancing the shaft, especially long shafts. It minimizes shaft whip when the anode wears unevenly..

If you were doing TWO on a shaft, I assume you put the other as close to the shaft tube as you can?

 

[Dan_Y]

Finally, as a follow-up to post #50, I replaced my bilge pump wiring and also replace the battery charger with a Pro Mariner. I may have had a ground issue there as well. Also added a third zinc (probably the biggest help). Also have heard that the fast tide flow thru the marina can contribute to zinc wasting. I have to replace two of the zincs at about 4-5 month intervals, which is probably about right. I polish the inside of the zinc and polish the shaft as Mainesail shows earlier in this thread. Interestingly, with the three, 1" egg zincs butted to each other, and with the aft zinc an inch from the cuttless, the two end zincs consistently waste faster than the middle one. I have a 3-blade bronze prop on an aquamet 19 shaft. So the middle one gets changed every other time. They seem to waste faster in warmer water, but that may be my imagination.

 

[jviss]

I inspected my new boat and found severe erosion of the hub-end zinc on my Max-Prop. The zinc was brand-new on Sept. 1, boat launched and then sailed to my new home port, at a mooring only until about Nov. 21. About a dozen hours of battery charging from 9/8 to 11/21.

I was shocked to see that the zinc is almost gone. All that remains is a ring suspended by the attaching screws. There are two zincs on the stainless shaft, one eroded a bit, the other not much at all.

Any clue as to why this would happen?

p.s. I didn't install the zinc, the boat yard where I bought the boat did.
p.p.s. duh! didn't measure, what size zinc do you think I need for this?

 

[fstbttms]

p.p.s. duh! didn't measure, what size zinc do you think I need for this?

What's your shaft diameter?

 

[jviss]

What's your shaft diameter?

Found it! Thanks. I just found the docs, it's a 63mm zinc.