If Yer Shaft Zinc Is Gone...?

[CSY Man]

If your shaft zink died and departed a month or 2 or 3 ago, what would be the damage?

Just a pitted prop, or more serious stuff?

(Moderately active area, not a marina with stray currents.)

[skipmac]

Prop is the most likely problem area. Check for loss of metal usually starting at the tips of the blades. Not visually obvious unless it's really bad. Polish the blades and look for a pinkish color on the blade tips. Also tap with a metal object and listen for a nice ring or a dull sound, changing as you go toward the tip.

[CSY Man]

Thanks.

Hopefully no damage yet.
Been too lazy to go down and look, but diver said zinks were gone.

Should hang a zink grouper over the zide with a wire to the shaft.
Had an old one laying around..Will look for it.

[Alan Brown]

The bronze prop strut on my 1981 Hunter 30 broke twice, most likely due to electrolysis. The first time I had it repaired. The second time I was forced to have a new one cast. As far as I know, the prop is the original one and still looks as good as new.

I doubt if your boat suffered any serious damage if you had no zincs for a short period of time. You'd be smart to replace them when you get a chance.

[sailorboy1]

if you have zincs in your engine heat exchanger, it's time to check them!

[Hydra]

It might be useful to have more than one zinc in the water. I have three: one on the propeller hub, one on the shaft forward of the strut and a big one on the hull, connected to the engine by a wire. Then, if the zinc on the propeller comes undone from vibrations, the others are still in place.

It's possible to put new zincs by snorkeling. I already dit it twice. For the one on the propeller, it's easy: you just have to hold the zinc, the screw and the wrench. It's more difficult for the zinc on the shaft: it's in two parts and there are two screws and two nuts. The first time I tried, one half of the zinc sunk. Now, I tie safety lines to the zincs and the wrench!

Alain

[Blue Stocking]

Be careful grabbing metal parts under water, and definitely not in marinas.
Make sure no AC is powered up.
A 1/2 volt DC can cause diaphram spasm and drown you.
Not a doctor, but have seen some strange things in marinas.

[Hydra]

Blue Stocking,
I already avoid diving in marinas, for other reasons that electricity. I retain your suggestion of disconnecting DC power when diving.

Alain

[sailvayu]

Just hanging a zinc over the side is useless unless it has a low resistance electrical connection to the metal it is protecting even then the distance from the protected metal could effect its usefulness.

Fair Winds

[CSY Man]

You'd be smart to replace them when you get a chance.

Did it when the diver found the zink gone..WIll not knowingly let the boat sit unprotected even for one day.

Just hanging a zinc over the side is useless unless it has a low resistance electrical connection to the metal it is protecting even then the distance from the protected metal could effect its usefulness.

Yeah, I hook the fish up to the propshaft, otherwise it won't do nothing..
(got that one figured out )

if you have zincs in your engine heat exchanger, it's time to check them!

Yup, they are part of my maintenance program, do it once a year, a pencil zink on the heat exchanger and another pencil zink on the raw water system bonded to the engine block.

Thanks for the help and suggestions guys.
The zink issue took me by surprise, I never leave 'em on long enough to fall off and usually check 'em twice a year and replace once a year.
This time the shaft zink was gone, so was the 2 rudder bearing zinks.
Must have been some stray current or something, I don't leave my boat boat plugged in to shore power so I doubt I killed my own zinks.

Guess I will have to check every 3 months now instead of every 6...

[HiZ]

Originally Posted by CSY Man

If your shaft zink died and departed a month or 2 or 3 ago, what would be the damage?

Just a pitted prop, or more serious stuff?

(Moderately active area, not a marina with stray currents.)

Metal will constanly exchange electrodes in water.
So, when dissimalar metals are submerged the softer of the two will loose to the harder of the two.
So, this is why anodes are made of soft metal.
They Loose.
Any metal that is down there is subject
So, what ever is now the softest will be the new Anode

[CSY Man]

So, what ever is now the softest will be the new Anode

What if you had a SS prop on a SS shaft with SS thru holes/sea cocks.

Same grade on the galvanic scale and no deterioation, or all the metal slowly but surely goes to he!!..? (Still need zinks?)

[fstbttms]

Originally Posted by HiZ

Metal will constanly exchange electrodes in water.
So, when dissimalar metals are submerged the softer of the two will loose to the harder of the two.
So, this is why anodes are made of soft metal.
They Loose.
Any metal that is down there is subject
So, what ever is now the softest will be the new Anode

Ummm... not quite. Hard or soft has nothing to do with it. Position on the periodic table has everything to do with it. Zinc anodes give up their electrons because they are lower on the periodic table or less "noble" than bronze or steel.

[fstbttms]

[QUOTE=CSY Man;448726]

What if you had a SS prop on a SS shaft with SS thru holes/sea cocks.

Same grade on the galvanic scale and no deterioation, or all the metal slowly but surely goes to he!!..? (Still need zinks?)

Zinc anodes (there is no "k" in zinc, BTW) protect metal parts from other forms of corrosion besides galvanic. Bottom line- you need to have them.

[cal40john]

Originally Posted by fstbttms

Ummm... not quite. Hard or soft has nothing to do with it. Position on the periodic table has everything to do with it. Zinc anodes give up their electrons because they are lower on the periodic table or less "noble" than bronze or steel.

Almost, it's the galvanic table, not the periodic table, and if you look at the order of the galvanic table it doesn't relate to the periodic table in any easy to see correlation. I believe it's fairly complex, I don't remember coming across it in chemistry other than as a list.

Galvanic Series

John