Karl Weinert writes a regular Column titled;
A Grain of Truth all about wooden boats for ClassicYachtMag.com

Electrolysis Part II - It’s Scary!
By Karl Weinert

After reading last month’s article on electrolysis and how it effects your boat, you may think there is no way to keep your boat floating. Or you may think because you have a wooden boat, you shouldn’t have to worry about electrolysis right? WRONG! Nature has a way of evening all things out [through electrolysis], but there is a way to keep your boat intact and floating for a while… say many years. If you run your boat in salt, or brackish water all this information is critical. If you use your boat in fresh water, the zinc will disintegrate, just more slowly.

Here’s a brief update on last month’s article (I hope that the editor will be able to add a link here so people reading this for the first time can go back to the previous issue allowing you to read); Part I on Electrolysis, it’s that important.

Electrolysis is electrical current created by different metal fittings on your boat, on the hull, under water. The more noble metals will last and the less noble metals will disintegrate; depending where the fittings are on the boat bottom it can be very costly. For example, Cris Craft originally used brass screws on the bottom, recently a boat was brought to me after a boatwright repaired a Cris Craft bottom using all stainless steel screws. You never mix brass and stainless screws on the hull underwater, it is a perfect recipe for electrolysis. Have you ever heard someone say ‘their boat just sunk at the dock, for no reason?’ Well it could very well be due to electrolysis. Electrical current might be traveling through the water from a neighboring boat several slips away and attack your boat. If your boat wiring is not set up correctly, then the fittings will not be protected from electrolysis.

The most ideal scenario is to use all the same metal for fittings throughout for all parts. As ideal as this is, it is not practical…and would be expensive too.

There are bronze props, stainless shafts, bronze rudder, and bronze thru hull fittings. Even if you bought all bronze fittings ‘off the shelf’, the internal makeup of each component could be manufactured with different compositions of bronze.

In addition to the internal make-up of bronze could be different, piece to piece; there is silicone bronze, aluminum bronze manufacturers even make parts that look like bronze but are red brass [mostly pipe nipples and elbows]. Some places you just can’t be sure what you are getting, better supply houses will tell you what your pieces are made of, make sure your boatwright buys from the better supply houses. Ask where s/he buys the fittings. If you can not get answers go else where.

With metal in boats and boats in water there is always a potential for electrolysis which creates havoc on our boats. To keep everything safe, boat owners put sacrificial zinc somewhere on the boat bottom. The sacrificial zinc erodes away during electrolysis, protecting the bronze and stainless steel fittings. This is a good thing.

It is still best to use ground wires in wooden boats. Wet wood will conduct electricity, but you can’t depend on it to protect your underwater fittings. You can’t depend on wet wood. If you’re wondering if you have to ground every silicone bronze screw holding the boat together – well that’s not practical. Suffice it to say that all wooden boats over time will need refastening; and we’ll rely on the wet wood as a conductor for the screws. Glass hulls must use wires because fiberglass is not a good conductor.

Figure A, is a birds eye view looking down through the hull. (Click image to enlarge)

By placing the sacrificial zinc on the bottom of the boat near the transom, you can reach down and feel if it is still there doing its job. Most people believe placing the zinc on the rudder is best, but you can’t easily reach it to feel how much zinc is left, so this is not your best choice. If you place the zinc on the rudder, it affects your steering, not good. I lived in Florida for many years and while swimming off the boat, it was easy to check the zinc and replace it even while the boat was in the water. By viewing Fig A, this should help you see where to attach the sacrificial zinc in a more convenient place, [rather than the rudder] which will be easier for you to keep your eye on and replace it as needed.





Figure B. [is an enlargement of the rudder port from Fig A]. (Click image to enlarge)

This rudder port drawing shows a coiled wire for a ground wire. Attaching wire this way allows the rudder to turn without breaking the wire. You still need to frequently check your ground wires for breakage. Vibration and corrosion also cause breakage.










Fig C. (Click image to enlarge)

The Shaft Rider diagram shows all grounding wires in this location. The brass shaft rider can be positioned in any convenient position as long as it has pressure against the shaft for good electrical contact.

You might think the boat is protected because the prop and shaft are bolted to the transmission which is iron and steel. Not true. The transmission shaft rides on bearings. The purpose of the oil in the transmission is to reduce friction and cool the parts to avoid burning-up the parts. While the oil is doing its job, the bearings sit in a film of oil, insulating the shaft from the housing. The result is the shaft is unprotected, it is not grounded. To correct this, you need a direct ground on the prop shaft.

A shaft rider is just a piece of brass approximately 1/8” x3/4” by 8” long; and it is bent spring loaded to the shaft. This is just like a DC motor brush. Do not oil on the rider because it will insulate it from the shaft. Truth be known, I did use a single drop of oil every-once-in-a-while, because it squealed more than I could stand. I never had a problem in the salt waters except if I forgot to renew the zinc. If you are feeling for the zinc and not much is there – just replace it in the same place because that means it is doing what it is placed there to do --- protecting your boat bottom.



Fig D. The Zinc Grounding diagram (Click image to enlarge)

Illustrates two methods to get the ground wire connected to the zinc thru the outside of the hull [which is in the water]. You may have to drill the zinc to suit your thru bolts. Choose one method or the other and try it.

Now the sacrificial zinc only protects your boat hull fittings from electrolysis, not things you might hit accidentally causing damage to the bottom while cruising the waters.

Zincs are very inexpensive $3 - 4.00 each and found at most marine supply stores. These are cheap enough to have atleast an extra one or two on hand.

If you have trouble finding zincs – email or call me.

Boat ownership, care and maintenance always require a vigilant eye. This system of wiring to prevent electrolysis has worked for me for years, on all my boats. It is what I do to protect my boats, and what I recommend to all my boat restoration customers. Of course there are no guarantees – only death and taxes are guaranteed.

Hope you enjoyed this article – see you next issue. Keep those emails and questions coming.

Sincerely ~
Karl Weinert
1327 Prince Rd
Big Sandy, TN 38221
KarlWeinertBoatWorks.com
boatsbykarl@gmail.com

- my motto –

“anytime you get back to the dock, it’s a good trip!”

P.S. I am now accepting reservations for the next wooden boat restoration. If you have a boat that needs restoration call me and we’ll discuss it.