Zinc Anode Troubles

[ambloplites]

I have a question/dilemma, and am hoping folks out in ether-land might have some experience with this.

I'm purchasing a Young Sun 35. She's a full keel, similar in many respects to a Tayana 37 ... just a bit shorter.

We had her hauled for inspection/survey last week ... mostly all is good, except that the zincs are not functioning/bonded. The zincs looked brand new, and the propeller was basically toast (been acting as the anode for the last year or so). Amazingly though, the prop still pushed her around pretty well, even though two of the blades were really only about 1/2 blades! At least that's good to know!

The surveyor threw out some options to remedy this. First of all, there's no room on the shaft for "shaft zincs". One option was having a "hub" zinc installed and the other was having a "divers dream" hull plate anode installed. I'm not terribly familiar with either, and was wondering if anyone out there has had either installed ... what it might cost ... are you happy with their performance ... etc.

Of course, my preference is to know why the original zincs aren't bonding ... surveyor said he couldn't see where the bonding was supposed to occur ... I'm wondering if somehow it's been "destroyed" over the years.

Thanks very much for any words of wisdom.

Phil

[donradcliffe]

and where were the original zincs?

[zeehag]

on my prop shaft i use a collar zinc as the space between prop and hull is so small, a streamlined zinc wont fit.
i dont use hub zincs.
i do have 2 trawler plate zincs on my hull for bonding rudder bits

[fstbttms]

Most Tayana 37s use a "limited clearance" collar zinc on the shaft, so maybe your boat does as well. You need about 1.5" of exposed shaft to mount this zinc.



Tayana 37s have a 1.25" diameter shaft. You probably have the same, but if by chance you have a 1" shaft and too little room to mount a standard limited clearance collar, you can make a 25mm Beneteau "donut" collar zinc work. It is even thinner than the limited clearance zinc.

[senormechanico]

I installed a flexible coupling between the transmission and prop shaft for enough space to install a conventional shaft zinc ahead of the prop.

I also installed a centrally located zinc which is bonded to all thruhulls and my refrigeration underwater heat sink.

[rw58ph]

Why not run new green wire and re bond to the present zincs. Several years ago I ran new green bonding wire as the older wire was in poor shape. At the same time when we pulled I added a big diver dream zinc for the bow thruster.

My diver told me the shaft zinc would probable not last through the winter, but he could not get the old one off. So I have a Grouper Anode zinc that has a clamp to connect to the shaft, 12 ft wire that is hung over the side into the water. I also have one connected to the Perkins gne set. I like the Grouper as its easy to check as i can not see big hull zincs. Also chekc the engine zincs.

Anyway I would at clearn, repair, and use the existing/present zincs and added if necessary.

[ambloplites]

Don - I honestly don't know exactly where the original zincs are located. Unfortunately I could not be present for the haul out and survey (a true bummer for me). I believe that they are located on the rudder, just below the prop ... similar to a Tayana.

Zeehag - thanks for the info!

Fstbttms - thanks for the info! I was just looking at the thinner Beneteau donuts ... might be an option ... or at least a short term solution.

RW58PH - not sure if the green wire is still present or not ... or what condition it's in. However, I was also thinking about this.

Right now, she is supposed to have a "grouper" or "guppy" zinc dangling over the side (for stop-gap protection). I'm going to have her hauled back out for prop replacement soon, and should have a better idea of what to do then.

Thanks folks for the quick replies and ideas.

Phil

[djmarchand]

Phil:

Here is one way to solve your problem.

First install an internal bonding system. From each underwater bronze fitting, hook up an 8 gauge wire and "daisy chain" them together so that each end of the loop attaches to the engine block at its DC ground point.

Then install zincs on the prop shaft, or prop end as appropriate, one on the rudder (only if it is bronze) and one large hexagonal plate zinc on the transom. Make sure that the transom zinc is part of the bonding loop.

The prop end zinc can be installed with a special prop nut with an extended cage that lets a tapered zinc slip over it and attach with a screw on the end. Go to boatzincs.com and look these up.

Some will say that a bonding system is worse than none. Almost all new boat builders install one, so I would go with that.

David

[fstbttms]

Originally Posted by djmarchand

Here is one way to solve your problem.

Then install zincs on the prop shaft, or prop end as appropriate...

If the Young Sun 35 is very much similar to the Tayana 37, there isn't enough space between the prop and rudder to install a prop zinc.

[a64pilot]

I'm not real sure exactly how, but do know that if your slip mate's electrical system isn't up to snuff, it will cause accelerated electrolysis on your boat. Of course you need to replace zincs, but keep an eye on them to see how fast they are being eaten away.

[Celestialsailor]

There is a strap device which lies on the prop shaft internal to the boat. Then that is bonded to a zinc plate nearby on the outside under water of course.
Here is a link.
Professional Mariner, Shaft Brush Grounding Device

[sailorboy1]

get a new prop and look into the thin zincs and plan on replacing them often

BTW - I don't really understand what some of you are talking about in this "bonding" thing. Installing a zinc on the shaft inside the boat is worthless. The zinc has to be in the water and there has to be a low resistance electric path between the shaft, prop, zinc or the the whole thing is just unless. Bonding on a boat is something completely different than zincs for galvanic corrosion protection.

[boden36]

Celestial Sailor has the right idea. It is really easy to make up a brush holder to accommodate whatever old starter motor or generator brush you can find. You can even just mount a springy piece of aluminium or brass so it rubs on the shaft.
If it is rubbing on the prop shaft, and electrically connected with an anode on the outside of the hull, it will protect the prop.
Regards,
Richard.

[FlyingCloud1937]

One thing to remember is about 90% of stray current corrosion damage is a result of the own boat. This is especially true of salt water moored boats.

Adding to much zinc to a wood or fiberglass boat with wood coring can cause serious structural damage, by zinc burn/de-lignification.

Daisy chained bonding systems can be a big offender. If one of the connections in the circuit is high resistance, the stray current can leave one fitting and jump bypassing the high resistance fitting.

If your bonding system is daisy chained, you should re-new each connection at least every five years, and more if they are located in the bilge and contact bilge water regularly.

Do to the damage to the prop of the OP, it would be advisable to have a qualified corrosion survey done. That 300-$500. dollar cost can save many thousands of dollars.

Lloyd

[Celestialsailor]

Originally Posted by FlyingCloud1937

One thing to remember is about 90% of stray current corrosion damage is a result of the own boat. This is especially true of salt water moored boats.

Adding to much zinc to a wood or fiberglass boat with wood coring can cause serious structural damage, by zinc burn/de-lignification.

Daisy chained bonding systems can be a big offender. If one of the connections in the circuit is high resistance, the stray current can leave one fitting and jump bypassing the high resistance fitting.

If your bonding system is daisy chained, you should re-new each connection at least every five years, and more if they are located in the bilge and contact bilge water regularly.

Do to the damage to the prop of the OP, it would be advisable to have a qualified corrosion survey done. That 300-$500. dollar cost can save many thousands of dollars.

Lloyd

This is exactly the reason I have never bonded in 35 years of owning boats. I have an RF copper plate for the Ham under the water and it is bonded to a zinc only. This is because it's fasteners are dissimilar metals. I have an end zinc on the end of the prop shaft. Be careful with those. I lost 2 of them in 200 miles until I ordered the diver to seat it on with a hammer and then tighten the end machine screw. Seems the cavity for the prop nut in the zinc is tapered to allow it to come out of the foundries mold easier. But this is a problem for the nut to get seated apparently.