Not so pretty in pink...

On my previous boat I rigged a wire w a clip on one end for the propeller shaft and a piece of zinc on the other. Would attach it to the shaft (when in harbor) and put the zinc over the side and submerged several feet. Would need to remember to remove the clip when getting under way. I now use the "zinc bullets" that SCOTTEDAVIS posted and wonder if the over the side wired zinc would help save the "bullet"? Now I've got the "Barnacle Buster" coating on my prop. I know one can get over zinced.
I drilled a hole in the rudder to extract the prop shaft and plugged it w the piece that came out w the hole saw using three carriage bolts.

Re Peter B's comments I replaced the original prop on our 40 yr old boat just 2 or 3 years ago mostly because I wanted the style of prop in the picture.

My shipwright works on a lot of the commercial boats in Steveston. While they are in the hard getting work done, he pours molten zinc into a "sandwich mold" around the prop hub. The molten zinc infiltrates all of the "prongs" on the hub. A tiger torch is used to remove the spent zinc. He goes about the yard recycling the old zincs as part of this process.

I used a ready-made prop "bullet" last time, but I think I'll see if Murray can "molten zinc" thing next time.


Jim
Sent from my iPad using Trawler Forum

RT Firefly said:

Greetings,
Mr. F. Did you use conductive epoxy? If not, have you checked the continuity between the "business end" of the brush and your grounding system?

Click to expand...

RT, good question. Actually the "leads" are embedded in the brush, so I felt that having them fastened to the bonding wire with a bolt and nut would assure continuity.
Friday the yard finished the bottom paint and replaced all zincs except for the prop shaft 1 3/4" ones that are ordered for Monday. He assured me he would sand/ polish the paint off before mounting the zincs. I never mentioned to him I had the shaft brushes- figured the bolt on's would give some added protection.
I actually don't know how to determine if my bonding system is doing the job other than what appears to be normal wear patterns on the block zinc.
Wouldn't mind some advice on how to do it.


1983 Present 42 Sundeck
Twin Lehman 135's

Forkliftt said:

RT, good question. Actually the "leads" are embedded in the brush, so I felt that having them fastened to the bonding wire with a bolt and nut would assure continuity.
Friday the yard finished the bottom paint and replaced all zincs except for the prop shaft 1 3/4" ones that are ordered for Monday. He assured me he would sand/ polish the paint off before mounting the zincs. I never mentioned to him I had the shaft brushes- figured the bolt on's would give some added protection.
I actually don't know how to determine if my bonding system is doing the job other than what appears to be normal wear patterns on the block zinc.
Wouldn't mind some advice on how to do it.


1983 Present 42 Sundeck
Twin Lehman 135's

Click to expand...

Get a multimeter, switch it to ohms, put one lead on each metal you are concerned about and measure the resistance. You should get a reading of 0.05 or less, 0.00 is best. The higher the reading the more resistance (less continuity).

greetings,
Mr. Fork. Ahhhh....Re-read your post. I had missed the mention of the pig tale-apologies...

JDCAVE said:

My shipwright works on a lot of the commercial boats in Steveston. While they are in the hard getting work done, he pours molten zinc into a "sandwich mold" around the prop hub. The molten zinc infiltrates all of the "prongs" on the hub. A tiger torch is used to remove the spent zinc. He goes about the yard recycling the old zincs as part of this process.

I used a ready-made prop "bullet" last time, but I think I'll see if Murray can "molten zinc" thing next time.


Jim
Sent from my iPad using Trawler Forum

Click to expand...

Zincs are comprised of other ingredients (alloys) when they work they give up ingredients, melting down whats left will not give you a new good replacement.

I would not use a zinc re-melt, I think the China zincs are made better and they are junk.

" Canada Metal zincs are composed of an alloy that meets Mil-Spec MIL-A-18001 for sacrificial anodes. This alloy is mostly zinc, but with measurable concentrations of cadmium (~0.1%) and aluminum (~0.25%). The additional cadmium causes the anode to erode from the surface inward, which causes a ''sandblasted'' appearance to the surface. When the anode is almost dissolved, it needs to be replaced."

I'm not so sure that's the case, Scott, otherwise there'd be a lot of unhappy fishermen about! it's a pretty common procedure around the commercial waterfront. One would think that otherwise there would be a problem with oxidation of a lot of props out there. Murray would have learned this procedure from veteran shipwrights 35 years ago when he apprenticed with Canadian Fish. I've watched him do this and the slag separates from the liquid metal.


Jim
Sent from my iPad using Trawler Forum

Like many things I life...there's high grade and low grade....

My bet is smelting of used zincs may work.....but it's like spraying oil on an old road instead of new asphalt. It may work...but just barely.

Smelting new zinc alloy would be OK....but is it new or old, depleted zincs?

....have to agree that as a zinc depletes.....what is left isn't what you started with....I think but could be wrong..

Okay, so think about this a bit more....

You've got the best zinc in the world. Maybe it's got a bit more Cadmium or Aluminum or whatever, but...it's held on...with a screw?!?! It fits fine when you put it on but next year when you take it off, is it secure? How many loose zincs have you seen when you take them off? Now compare that to a process where molten sacrificial anode is pored around the prongs on the hub of the propeller. It takes a tiger torch to remove the material.

Don't know for sure but I think I'll trust the shipwright.


Jim
Sent from my iPad using Trawler Forum

boatpoker said:

Get a multimeter, switch it to ohms, put one lead on each metal you are concerned about and measure the resistance. You should get a reading of 0.05 or less, 0.00 is best. The higher the reading the more resistance (less continuity).

Click to expand...

Boat poker, sorry I don't quite follow. I know if I want to be sure my prop shaft has continuity through the brush and to the bonding wire I would measure resistance between the shaft and the bonding wire. Is that what you mean? I wonder if there is an easy way to be sure there is minimal resistance from say- the prop shaft to the big zinc block ?


1983 Present 42 Sundeck
Twin Lehman 135's

Don't believe it but we were told by the yard that once a zinc is out of the water it is no longer useable. Anyone else ever heard that? I'm talkin' salt water here.

Click to expand...

This is 100% untrue. Because our harbor usually has a layer of fresh water on the surface, many of us hang a zinc on a cable (battery cable gauge) down about ten feet which puts it in normal salt water. The other end of the cable is connected to the boat's bonding system. This is because many boats like ours have transom zincs ("license plate" zincs) that are just below the surface of the water. This puts them in fresh water much of the time and they are not as effective. We pull the zinc up and stick it in a bucket on the aft deck when we take the boat out.

For our cable zinc we use old transom zincs that we get free from the dive service in our harbor. They are zincs they've removed from boats when they install new ones during scheduled routine hull checks and zinc replacements.

They don't last as long as a brand new zinc, but they're good for a couple of months and they're free. These zincs have been out of the water for months probably, in the recycle bin at the dive shop. They work every bit as well as brand new ones when we put them back in the [salt]water on the end of our cable.

Ancora, I read through this thread and closely viewed your pictures.

IMHO:

- Take the plunge, so to say. Pull both props and get them checked out by a reputable prop shop. Then, take actions accordingly. That will be best for you in the long run (maybe in the short run too - ya just never know). A boat dollar or two or three at this time could save you many, many added boat dollars and a lot of headaches in the near or not too distant future.

- Place at least one and preferably two two zincs on each shaft, one on each strut and one on each rudder. Your bonding system helps... but is no where near as good as anodes' surfaces firmly attached to diodes' surfaces. Over zincing can be accomplished... but that is only under rare circumstances and with a hell of a lot more zincs than mentioned here.

- Go boating with peace of mind!

Art

A DMM can be used to check continuity of the zinc to the metal it is supposed to protect when the boat is out of the water. In fact the resistance should be checked. Failure to do that may result in a zinc just looking pretty yet doing nothing. If zincs have not degraded or minimally degraded then be suspicious.

Sometimes even what looks like a clean mounting surface is not as clean as you think. I DMM check all my zincs and sometime find that one of them, even though TIGHT on the shaft or the steel keel, is not actually in contact. I now take my grinder or Scotchbrite to the zinc surface, lightly, so it is bright, and if need be hit the mounting surface with a Scotchbrite pad, wire wheel or sanding disc as needed.

I check the prop to shaft resistance also although I've never had a problem there. Yet the possibility exists that even with a brush and shaft zincs that the connection will not allow them to work.

http://www.boatzincs.com/corrosion-reference-electrode-specs.html

will take you to a silver-silver chloride half cell that is used in conjunction with a meter to take voltage readings of the metals immersed in seawater.
There are voltage levels for bronze, SS, Alum., and steel and the reading will give you a good idea of how they and the zincs are doing.

You will need your own DMM, and a long ground lead that is used to touch the metals to get the reading. The CELL goes into the seawater.
I bought the meter kit years ago. I didn't know about Boatzincs at the time so spent a lot more money that I would have to now.
So assuming that most of us have a DMM and can cobble a 20ft probe lead this is one way to go.

I check my voltage levels at least twice a year. A couple of times I found a piece of metal that was not being protected so was able to take action rather than waiting to find out at haulout.

The setup can also be used to check for AC leakage. By disconnecting shore power and testing, then replugging shore power, if all is well than there should be NO change. If there is you may have a problem. You can also check to see if any AC ripple shows with a DMM which is another way.

I would get those props checked. Diver. But also ensure there is zincing that is actively protecting the props. They may be good with just a light pinking and if dealt with properly now could save you a bunch of money down the road.

I also have the half cell that plugs into my DMM and use it whenever I cannot get the Ever-Guard meter to read in the green. High readings usually means I have to clean the shaft wipers. Sometimes the diver is remiss in his duty to replace the two plate zincs on the transom. I buy the plate zincs from Boatzincs.com and leave a pair of them in my open dock box for the diver.

Great info. Thanks for sharing!


1983 Present 42 Sundeck
Twin Lehman 135's

Forkliftt said:

I still had the stainless arms left to our shaft "brushes". I took an electric forklift motor brush (same as a starter brush) and epoxied it to the arm. I drilled a hole in the arm, and used a small bolt to fasten the pigtail from the brush to the bonding wire. Has worked fine (I guess) for a couple of years. Will shoot a pic Sunday when I go to the boat.


1983 Present 42 Sundeck
Twin Lehman 135's

Click to expand...

Sorry- not a stainless arm. Here's the pics.


1983 Present 42 Sundeck
Twin Lehman 135's

Quick test of shaft brushes is to put the DVM in volts and measure between bonding circuit and shaft. A good connection is in the few millivolts. 100+ mV and you have poor connection.

You can't test using ohm meter in the water as there is an impressed voltage.

Forkliftt said:

Sorry- not a stainless arm. Here's the pics. View attachment 37198View attachment 37199


1983 Present 42 Sundeck
Twin Lehman 135's

Click to expand...

I would replace that connector with a marine grade heat shrink sealable one that won't corrode in a couple of months, to mention the wire which would have to be replaced too.

Ski in NC said:

Quick test of shaft brushes is to put the DVM in volts and measure between bonding circuit and shaft. A good connection is in the few millivolts. 100+ mV and you have poor connection.

You can't test using ohm meter in the water as there is an impressed voltage.

Click to expand...

Ski, unfortunately all I have is an analog meter today at the boat. Will grab my Fluke when I return next and test as suggested?

4712- that install is about a year and a half old- but will put the upgrade on my list.
Interesting story- recently at the local chandlery here in Gulfport I was asking for some bronze cotter pins (still had original ones installed) to secure the handles on the tapered cone sea cocks I am lapping in tonight. Poo Hoo I was told. Doesn't matter. I encouraged him to check in the Donovan Marine catalog- and none available. Went home with SS ones which I will install tonight.
All that to mention that last weekend in preparation for the bottom job I am having I was removing the "clam shells" that I could, the one for the AC strainer (apparently added later) one was actually secured to the mushroom head, as a set, with countersunk SS machine screws. And no problem to remove after all these years. Who woulda thought it??


1983 Present 42 Sundeck
Twin Lehman 135's

JDCAVE said:

I'm not so sure that's the case, Scott, otherwise there'd be a lot of unhappy fishermen about! it's a pretty common procedure around the commercial waterfront. One would think that otherwise there would be a problem with oxidation of a lot of props out there. Murray would have learned this procedure from veteran shipwrights 35 years ago when he apprenticed with Canadian Fish. I've watched him do this and the slag separates from the liquid metal.


Jim
Sent from my iPad using Trawler Forum

Click to expand...

Ok, boats cost money, zincs are.... well cheap in the overall scheme of things.

Fisherman are cheap, I know, I am one and when I ran a commercial boat (Dive) I was the cheapest. Now I think I will buy zincs that are Mil-spec and new. Your mileage may vary.

Regards

I stand corrected: I phoned my shipwright last night to discuss the process he uses for the zinc on the prop nut. Murray uses a new prop zinc, of a type that must be installed using molten zinc. It has a hole on the top to introduce the molten zinc. I had thought he was using a mold, but actually tongs were used to hold the zinc in place during the process. He's agrees that prop zincs that are 50% spent are compromised metal.

The reason for this more involved procedure is because the troll fishermen are concerned about the electrical potential of the fishing gear. Fishermen WANT to maximize the electrolysis of that zinc and they test the voltage gradient between the rudder and the fishing lines on the gurdies. Sometimes he uses spent zincs as a source of metal for the molten zinc and sometimes he uses new zinc-it's the fisherman's choice. Tuna fisherman are especially concerned about the electrical fields around their fishing gear.

I had forgotten that about 40 years ago, there was a lot of speculation about the effects of weak electric currents on the fishing catchability of fishing gear. A co-student of mine, Dan Nomura did his masters thesis on this area of research: "The effect of weak electrical fields on troll success for spring (Oncorhynchus tschawytscha) and sockeye (Oncorhynchus nerka) salmon." Fishermen used so called "black boxes" to control the voltage gradients between the fishing gear and the boat. The results demonstrated significant increased fishing success in certain situations, see reference for details. Incidentally Dan went on to become president of Canadian Fishing Company.

https://circle.ubc.ca/handle/2429/21785?show=full



Jim
Sent from my iPad using Trawler Forum

Pictures: the wipers on our twin screw trawler, along with the Ever-Guard meter and test gear. The only problem with Ever-Guard is not the system itself but ignorant divers who do not have a clue how it works, and want to add zincs.

Ancora- If your props are pink due to de-zinc'ing in the alloy, your Ever-guard system is not working, somehow.

IMHO and going back into the 1950's. Boat repair yard On LI, NY had a great sign over the door:


Zink or Sink!


True then... True today.

Forkliftt said:

Boat poker, sorry I don't quite follow. I know if I want to be sure my prop shaft has continuity through the brush and to the bonding wire I would measure resistance between the shaft and the bonding wire. Is that what you mean? I wonder if there is an easy way to be sure there is minimal resistance from say- the prop shaft to the big zinc block ?


1983 Present 42 Sundeck
Twin Lehman 135's

Click to expand...

1. Then simply measure between the shaft and to the point where your brush is bonded.

2. Measure between the shaft and the "big zinc block"

A few years ago I walked around a boat yard and measured resistance between shaft anodes and shafts. Out of 40 boats I found only two that had good continuity. One was a new boat that had never been in the water and one had just had a new anode (properly) installed. If your anode is not dissipating it is not working. Most people install anodes without ensuring continuity. The surface on which the anode is mounted must be cleaned and there must be good electrical contact between the two. Taking a wire brush to an anode is simply not good enough.

Ancora,
Ski is dead on.

Your Ever guard is not protecting the props. It may be working for other things but that pink says the props are not protected.

It may simply be that the shaft brush is not in GOOD or GOOD ENOUGH contact or the wire from the brush has a problem.

Even a wee bit of oxidation at the wire terminals or the terminal crimp barrels can cause trouble. The voltages are very small so ANY resistance can block the protection.

Check it out.

boatpoker said:

1. Then simply measure between the shaft and to the point where your brush is bonded.



2. Measure between the shaft and the "big zinc block"



A few years ago I walked around a boat yard and measured resistance between shaft anodes and shafts. Out of 40 boats I found only two that had good continuity. One was a new boat that had never been in the water and one had just had a new anode (properly) installed. If your anode is not dissipating it is not working. Most people install anodes without ensuring continuity. The surface on which the anode is mounted must be cleaned and there must be good electrical contact between the two. Taking a wire brush to an anode is simply not good enough.

Click to expand...

Well noted. I'm finally getting back to the boat today and the yard will have the zincs installed- I will confirm continuity with my Fluke. Thanks


1983 Present 42 Sundeck
Twin Lehman 135's

I took some readings today, and they were abnormally high. Cleaned off the shaft wipers and the readings went down to "acceptable." Gonna have to keep a closer eyes on them wipers.