Missing/lost prop zinc

[BaseCampAnne]

Cascadia was on the hard for two plus days immediately after Labor Day. I learned more about the zinc challenges after less than 6 months in salt water. The prop zinc was almost totally gone, and I had a long discussion with the Oak Harbor manager while my boat was being repaired.

He said that zinc had been ineffective for quite awhile already since there was next to nothing left. He also said it was not due to a missing lock nut since it was still attached. I learned that plenty of research has been developed by the military/ government on zincs for protection when multiple metals are used on boats. He suggested that there probably needed to be more discussion with the maintenance dept. at Ranger Tugs as to what is happening with new tugs. i.e. something else needs to be done so the existing zincs are not needing replaced so often.

One of his comments that I understood was that perhaps a medium sized plate-style zinc might be a good idea, but there seldom is a slam-dunk solution, rather a balancing act.

I believe someone reported changing zincs multiple times every year and the manager said that should not be necessary. I am now fascinated with the idea of placing 4 on the swim step connectors and also getting a galvanic isolator.

I was very grateful to see the zincs while the boat was out of the water and believe having a trailer would be very helpful. It seems that here in the Pacific NW in marinas at least some zincs are going to be needing replaced every 6 months as Ray reports.

I hope we continue to share experiences on this topic!

 

[knotflying]

I thought if the metal was isolated (not bonded to the boat's electrical system) that electrolysis was not possible. With that said, I would think that the swim platform supports are not attached to anything, hence not needing zincs to be sacrificed due to electrolysis. Anyone want to weigh in on this?

 

[trailertrawlerkismet]

I asked Andrew if I should ground the supports and he explained that I did not need to, however I can not recall why he said this. Maybe Andrew, if he reads this, will chime in. Barry, on Laxey, also installed collar zincs on his swim platform supports however he did bond them. Barry if you read this please give us your thoughts.

Jim

 

[Andrew Custis]

This is pretty tough to put it in words but I will give it a shot. Everyone has had great advice but I think we all agree that the learning curve with electrolysis can be a pretty steep one if you haven't done your research. With this post, I will tell you how we build our boats and I will tell you what "I" think you should do if you are keeping it in the water full time.

1. Install a galvanic isolator if you are keeping your boat plugged into shore power at least 50% of the time your boat remains in the water. I recommend using the Pro Mariner Fail Safe 30. Its inexpensive, reliable and safe. Pro Mariners customer service is hard to beat so what more could you ask for? The purpose for a galvanic isolator is to block any incoming stray current from other non protected vessels in your marina.

2. Install a grouper zinc or install a permanently mounted zinc plate on your boat that you tie in with the rest of your bonding system. As of now, all of you Ranger Tugs have a bonding system in place setup to protect the metals below the water line from electrolysis. The only way this becomes active is if you install a "Guppy zinc or Grouper Zinc" and attach it to your battery ground. Since the bonding system attaches to your battery ground, the guppy zinc as an inferior metal will start to attract the attention to it rather than your thru hulls, swim platform rails (if bonded), and other metals below the water line the bonding system ties into. A permanently mounted zinc plate does the exact same thing except you do not have to remove it from the water each time you use the boat like you would a guppy or grouper zinc.

3. The swim platform rails are not a bonded item on 2012 and previous model year Ranger Tugs. As Jim mentioned, its best to add a collar zinc to the rails OR bond them into your bonding system so your guppy zinc or permanently mounted zinc plate protects them.

4. Prop Zinc - The whole reason for a propeller zinc is to protect the propeller which I think everyone understands. A prop zinc disappearing is due to one thing, the marina your boat is sitting in. Since the propeller, thrusters and trim tabs do not bond into the rest of the bonding system, they require a zinc on each component. I think the reason you see a prop zinc disappear quicker than a thruster zinc is because of the amount of metal it is trying to protect. If you don't want to deal with a prop zinc, install a shaft brush. This is a device that allows you to make constant contact with the shaft that ties the propeller and shaft into the bonding system. Again, this would only be helpful if you had a zinc plate installed or a guppy zinc hanging overboard.

 

[BaseCampAnne]

Thank you, Andrew 🙂

As one whose boat is plugged in at a large marina with lots of other boats most of the time, I intend to have a zinc plate installed and perhaps the galvanic isolator. It also sounds like collar zincs for the swim platform are part of your recommendations, so they will probably be on my list also.

It is reassuring to read your comments and I believe they are in sinc with some of the advice I have heard. Electrolysis is still challenging, and your email has helped.

Thank you🙂

 

[Andrew Custis]

Anne,

I would recommend bonding the swim platform supports to the transom zinc you plan on having installed. Are you having Pacific Marine Center do this? If so, I would be happy to contact Bill and go over the system so he is informed of how we set it up. Hope all is well! Remember that you are welcome to call us anytime with questions.

 

[BaseCampAnne]

Thanks, Andrew, I will pm you.

 

[baz]

Based on Andrew's recommendation I will be bonding my swim step braces (that also have zinc collars) to my transom mounted underwater zinc plate which is in turn connected to a prop shaft brush that is also bonded to the boat's bonding system in the engine bay. One bit of advice if you want to install a prop shaft brush -- make sure you inform and ask any engine service technician to avoid treading on the brush attachment assembly. If necessary the brush can be disconnected from its spring and lessen the risk of being in the way.

Of course the best bonding technique for the swim step brace supports would be done on the inside (dry side) of the transom, but this could be difficult accessing the swim step brace mounting screws/bolts... so I may opt to string a good quality stainless steel wire between the braces on the outside and finally to the transom mounted under water zinc plate.

Since I did my extensive upgrades for improving/reducing the stock prop shaft zinc erosion last March I will need probably need until next March to compare my current zinc erosion data with previous year's data.

 

[baz]

Had the periodic diver inspection for my underwater zincs today.

Here's what the replaced prop zinc looked like after 3 months in salt water as compared to a new one. My guess is that the replaced zinc is around 40% to 50% gone. This tells me if the erosion is linear with time the zinc would be all gone after a total of 6 months from being new. As the zinc erodes its surface area diminishes so it becomes less and less effective presumably, and would erode more quickly.

I've been wondering how best to determine just how much zinc has been eroded compared to new. If I place each one in a kitchen measuring glass jug with volume measure lines marked on its side I could then compare each zinc's volume and I would assume this would be a good method.

1. Fill measuring jug with water and note its level as L1
2. Place new zinc in measuring jug and note the water level as L2
3. Replace new zinc in measuring jug with the old zinc and note the water level as L3

The percentage of zinc remaining would be... [ (L3 - L1) / (L2 - L1) ] * 100.

This assumes the old zinc, when new, was perfectly the same as the new new zinc. 🙂 ...and very little water was removed when the new zinc was removed from the measuring jug.

 

[knotflying]

Why not weigh it? wouldn't that give you the same results? Half the weight would mean you lost half the zinc, no?

 

[baz]

Why not weigh it? wouldn't that give you the same results? Half the weight would mean you lost half the zinc, no?

Yes, that would work as well so long as zincs have consistent weights. This is a simpler method. Thanks. 🙂

 

[baz]

Dup post... This happens when using mobile to post with.

 

[GulfSailor]

Why not weigh it? wouldn't that give you the same results? Half the weight would mean you lost half the zinc, no?

Yes, that would work as well so long as zincs have consistent weights. This is a simpler method. Thanks. 🙂

While they're unlikely to be identical, it's probably reasonable to assume that they at least have similar weight, density, and surface area, and it's only an approximate calculation that needs to be made to determine whether it's time for replacement or not, so I'd say use whichever is closest to hand, kitchen scales or measuring jug.

Just don't get caught messing up clean kitchen utensils with dirty old zincs. 😀

 

[mspaugy]

How expensive is that zinc? Is it worth all that trouble?

 

[knotflying]

We buy $200,000 boats and can afford them because we have been frugal. I see this same phenomenon with pilots; planes worth hundreds of thousands of dollars and they will tell you which airport they flew to to save .10 per gallon for fuel. :lol:

 

[baz]

My goal here is for determining the effectiveness of having added to my boat items such as a Pro Safe Galvanic Isolator, Prop shaft brush, transom mounted zinc plate, swim step bracing collar zincs and bonding the trim tabs to the transom mounted hinge plates.

Having done all that with some advice from Andrew and here on the forum I'm now in the process of determining the current zinc erosion compared to before all the above items were installed.

Being frugal is part of this activity, but the real challenge and interest for me is combating the zinc erosion. Two unknown factors are the effect of other boats nearby and the marina's electrical configuration changes over time. Other boats come and go and I have no clue what the marina might do with their electrical configuration over time.

The Galvanic Isolator was a freebie so its expense does not factor in. The other items cost me no more than $100. In the overall process so far I believe I now know more about galvanic activity than before I started investigating this issue.

I added all the boat mods to combat zinc erosion last March and I hope that by next March I will have enough data to show if zinc erosion has been arrested/slowed-down.

 

[baz]

How expensive is that zinc? Is it worth all that trouble?

I believe a prop zinc from Ranger Tugs Parts Dept is around $16. Replacing this twice/yr over say a 10 yr period amounts to $320. If one has a diver employed over this time period then add another $1000 to this number and you get $1,320.

 

[mspaugy]

When I do finally pull the trigger and purchase one of these fine boats mine will be on the trailer much of the time excpet for vacations and weekends here and there so replacing a $16.00 zinc occasionally and others doesnt seem too bad to me. I also plan on the guppy and galvanic isolator.

 

[baz]

I had underwater zincs inspected and replaced where necessary the other day... and this was after 3 months since last inspection.

Status today:
1) The propeller cone zinc & bow thruster zinc were 30% intact.
2) The stern thruster zinc was 50% intact.
3) The trimtab zincs were 65% intact.
4) The transom plate and swimstep arm zincs were 90% intact.
5) The bottom paint was considered to be in beautiful shape as was the running gear. (Bottom paint was redone last March)

I decided to have the prop zinc and the thruster zincs replaced as within another 3 months or sooner they would be gone.

-So far it seems my prop zinc needs replacing every 3 months just to be on safe side -- maybe I could stretch this to 5 or 6 months.

-Bow & Stern thruster zincs need replacing every 6 months.

-Trim tab zincs need replacing once per year.

-Have no reliable data for the swim step bracing collar zincs nor the transom mounted zinc plate yet.

Status 3 months ago:
1) The propeller zinc was 25% intact. Was replaced.
2) The thruster zincs were 70% intact. Were not replaced.
3) The trimtab zincs were 70% intact. Were not replaced.
4) The transom plate zinc was 95% intact. Was not replaced.
5) The swimstep arm zincs were 99% intact. Were not replaced.

Status 6 months ago:
1) The propeller zinc was 10% intact. Was replaced.
2) The trimtab zincs were 15-20% intact. Were replaced.
3) The thruster zincs were 40% intact.

 

[BaseCampAnne]

Interesting statistics and study you are doing on the zincs, Baz. I look forward to future results.

I am going to be interested in learning how the zincs last in San Diego. I believe the environmental standards are tougher in the marinas there, so perhaps the problems will be different, but I am becoming a skeptic. In addition, the water there is much warmer, which probably will have negative implications.

I am also guessing research results will always be dependent upon the marina, what the protections are for boats near ours, and how often other boats with problems are coming and going, sharing their "infectious" problems :-(

I have decided not to go with the galvanic isolator at this point due to the cost for having it put in, plus the 25 is a small boat. I am going to have a transom zinc put in, and have had the swim step bonded now, which should help.

I found it interesting that the 26 Cutwater comes with both the transom zinc and the bonded swim step, as I understand.

And the sacrificial zincs continue eroding...ah, what would we do if this were simple? :roll: