electrolysis & transom drains

[brooks&judy]

In Puget Sound and I presume in seawater elsewhere, there's a drive to replace creosote-impregnated wooden pilings to improve water quality. The most common replacement in my town are pilings of galvanized pipe. They've greatly increased electrolysis problems in our already 'hot' harbors.

The rudder zincs I put on my SS trim-tabs and the bar zincs under the outboard brackets fizz away like Alka-Seltzer on my 22 Cruiser. I asked a marine engineer about those steel pilings. He said they create incredible hot-spots in salt water in a roughly 4' radius around each pile. The effect reportedly tapers off further away, but is still harmful to more noble metals 12' or more distant.

I spun my C-Dory in its berth to get its rump around 20 feet from the nearest piling and the fizzing slowed but not enough: Trim-tab zincs top & bottom (3" dia.) last around three months, the bar-zincs on the motor brackets around six.

I decided to trailer-boat. When I pulled it out and scraped a bit of the transom drain tube with my pocket knife, it looked like copper - not good if it began life as brass.

Anybody know if those tubes in `06 C-Dorys were indeed brass or did they start life as copper?

I can't find any perforations in the tube - it's not turned to lace yet. For now I've coated the tube liberally with a lanolin-wax and intend to seal off the drain tube with an oval piece of Gorilla Tape over its outboard side in hopes of isolating it from seawater if I use the boat before replacing the tube with a composite.

I'm not used to having a transom drain and have never needed to use this one. I think I could push the Gorilla Tape off with a broom handle from inside the cockpit. I doubt I'll need to, having two electric pumps, a bucket, and likely soon a 10" diaphram pump.

Any words of wisdom from the more experienced?

Thanks!

~ Brooks

 

[Sunbeam]

If you'd like to see more about what the brass tube looks like (and how I eliminated it), you could look here in my Sunbeam ~ 22 Cruiser thread.

If you do have a tube, and it looks like brass, it almost certainly is. They are rather thin, and I'm not a big fan (although they obviously do the job on many boats). If nothing else you can see how it's installed and what it looks like.

The transom drain tube project starts at the third post down on this page:

http://www.c-brats.com/viewtopic.php?t= ... c&start=15

It peters out for awhile as I worked on other things, but you can pick it up again on page 8 of the thread, around four posts down from the top.

http://www.c-brats.com/viewtopic.php?t= ... &start=105

 

[Marco Flamingo]

I just replaced my spash well drains, and they were brass tubes. Hogged out the holes and epoxied 1.25" PVC DWV pipe into place. Nice color match. The transon drain looks the same, but I haven't gotten to that yet.

I've lived aboard in hot moorages and it's every man for himself. I would recommend buying one or two of the giant commercial zincs, sometimes shaped like a fish, that you hang overboard and clamp to your boat. They are usually 5# of zinc. Be sure to run some kind of a tag line from it to one of your dock lines or even the helm so that you can't forget about it when you cast off.

Mark

 

[rogerbum]

I just replaced my spash well drains, and they were brass tubes. Hogged out the holes and epoxied 1.25" PVC DWV pipe into place. Nice color match. The transon drain looks the same, but I haven't gotten to that yet.

I've lived aboard in hot moorages and it's every man for himself. I would recommend buying one or two of the giant commercial zincs, sometimes shaped like a fish, that you hang overboard and clamp to your boat. They are usually 5# of zinc. Be sure to run some kind of a tag line from it to one of your dock lines or even the helm so that you can't forget about it when you cast off.

Mark

It's completely unclear to me how you intend to bond this kind of zinc to the other metals on the boat. The way that zinc's work is that when they are attached to a more noble metal (one higher up in the galvanic series), the zinc corrodes instead of the metal to which it is bonded (e.g. electrically attached). Simply hanging a zinc over the side of the boat won't be helpful.

 

[SGIDave]

I just replaced my spash well drains, and they were brass tubes. Hogged out the holes and epoxied 1.25" PVC DWV pipe into place. Nice color match. The transon drain looks the same, but I haven't gotten to that yet.

I've lived aboard in hot moorages and it's every man for himself. I would recommend buying one or two of the giant commercial zincs, sometimes shaped like a fish, that you hang overboard and clamp to your boat. They are usually 5# of zinc. Be sure to run some kind of a tag line from it to one of your dock lines or even the helm so that you can't forget about it when you cast off.

Mark

It's completely unclear to me how you intend to bond this kind of zinc to the other metals on the boat. The way that zinc's work is that when they are attached to a more noble metal (one higher up in the galvanic series), the zinc corrodes instead of the metal to which it is bonded (e.g. electrically attached). Simply hanging a zinc over the side of the boat won't be helpful.

Hello Roger,

The "hanging" anode looks like this:

It is alligator-clamped to the negative DC buss or a negative battery terminal. The bonding system ultimately is connected to the negative DC buss, so this is how the hanging anode is incorporated 'electrically' into the system...SAME as the other zincs on the boat which are mechanically attached to metal on the boat.

dave

 

[rogerbum]

Thanks Dave. Of course unless the metal of interest (the splashwell drains in the quote above) are connected to the electrical grounding system, this won't protect them.

 

[thataway]

One question I would ask is if the anodes on the Honda were Zinc, Aluminum, or Magnesium? Honda makes all three, and of course it would vary as to the type of water as to which anode you are going to use.

Brooks&Judy, do you have 110 V AC on the boat? Is there a galvanic isolator? If the pipe is zinc coated (Galvanized), it would seem that that would be eaten first--rather than your zincs. Good galvanizing, will last a considerable time in salt water. The most common cause of corrosion in marinas is electrolytic rattan than galvanic, especially with steel pilings, because they are such a good conductor of electricity (incorrectly wired docks and boats).

Agree, that the "fish" anode is no good for the brass tubing. The brass tubing in the splash well should not be subject to electrolysis or galvanic action.

The galvanic chart:

There are times you will want to have a drain plug, especially with the boat on the trailer--to allow rain water to flow out of the boat. Even with a slant back, or camper canvas, some water may get in.

It is almost impossible to get all of the water out of the C Dory with a bilge pump. If you have two pumps, one should be back at the stern sump, and the second should be inside of the cabin, which is where the 2006 C Dory 22 has the factory pump. Although I have had the manual diaphragm pumps on some of my larger boats, I don't see the need for one in the C Dory 22. At times, I carry a Rule 3700 pump, with long leads, and a long hose, for dewatering. I have never used this on one of my boats, but on others. I do carry a cheap PVC "piston" type of pump--to dewater the cooler (if carried) and the dinghy.

Another option in bilge pumps is an electrical diaphragm type, which gets away from the back flow from the tubing. I have never liked the one way valves, and have removed them from the pumps on my C Dory.

 

[thataway]

One question I would ask is if the anodes on the Honda were Zinc, Aluminum, or Magnesium? Honda makes all three, and of course it would vary as to the type of water as to which anode you are going to use.

Brooks&Judy, do you have 110 V AC on the boat? Is there a galvanic isolator? If the pipe is zinc coated (Galvanized), it would seem that that would be eaten first--rather than your zincs. Good galvanizing, will last a considerable time in salt water. The most common cause of corrosion in marinas is electrolytic rattan than galvanic, especially with steel pilings, because they are such a good conductor of electricity (incorrectly wired docks and boats).

Agree, that the "fish" anode is no good for the brass tubing. The brass tubing in the splash well should not be subject to electrolysis or galvanic action.

The galvanic chart:

There are times you will want to have a drain plug, especially with the boat on the trailer--to allow rain water to flow out of the boat. Even with a slant back, or camper canvas, some water may get in.

It is almost impossible to get all of the water out of the C Dory with a bilge pump. If you have two pumps, one should be back at the stern sump, and the second should be inside of the cabin, which is where the 2006 C Dory 22 has the factory pump. Although I have had the manual diaphragm pumps on some of my larger boats, I don't see the need for one in the C Dory 22. At times, I carry a Rule 3700 pump, with long leads, and a long hose, for dewatering. I have never used this on one of my boats, but on others. I do carry a cheap PVC "piston" type of pump--to dewater the cooler (if carried) and the dinghy.

Another option in bilge pumps is an electrical diaphragm type, which gets away from the back flow from the tubing. I have never liked the one way valves, and have removed them from the pumps on my C Dory.

 

[hardee]

Bob, you said:

"..... If you have two pumps, one should be back at the stern sump, and the second should be inside of the cabin, which is where the 2006 C Dory 22 has the factory pump."

Is you forward pump, the one you are saying, I think, is inside the cabin actually set up to drain the cabin? On my 05, there is a pump, at the aft end of the "hallway" where there is a step and a small horizontal door over the "bilge", but that is set to drain the cockpit, IF the boat is loaded forward and the cockpit floor is then slopped forward so the aft pump and sump would be dry. The water access to that froward pump is through a slot under the door from the cockpit, not from inside the cabin side on my 22 Cruiser.

I learned that pump does not drain the cabin side one time after a rather vigorous washing process, with TOOOO MUCH water in the cockpit :shock: :lol:

Harvey
SleepyC :moon

 

[Marco Flamingo]

It's completely unclear to me how you intend to bond this kind of zinc to the other metals on the boat. The way that zinc's work is that when they are attached to a more noble metal (one higher up in the galvanic series), the zinc corrodes instead of the metal to which it is bonded (e.g. electrically attached). Simply hanging a zinc over the side of the boat won't be helpful.

On my C Dory, the transom plug is the only piece of submerged metal not connected to the engine. Bonding it to the engine or battery would be simple. And I would get one anyway. It is fairly common to have the bottom of the motor mounting bracket touching the water. Aluminum is lower on the galvanic scale than the transom plug. If the transom plug is showing bright copper, I'd figure out where to hang the zinc.

Mark

 

[brooks&judy]

Thanks Bob,
especially for the noble metals chart and the word on Honda anodes sometimes being other than zinc. `Never thought of that possibility! Now I get to decipher which is appropriate here. Assuming they're zinc anodes under the transom brackets, I'd vowed to buy stock bar zincs and cut & drill them to fit rather than pay a ransom for Honda's designer anodes. Perhaps I need another material? I'll check, thanks to your advice.

I think you're right in your argument for transom drains, thus will be replacing my 'brass' tube with plastic instead of blanking the hole. I'll inspect the transom core for moisture in the process, repairing as necessary. I may still install a manual 8" diaphram pump to dewater the cockpit, operated from inside the cabin for when the lower portion of the glass door appears to be part of an aquarium. I'll feel better then when exposed to the North Pacific.

I'm not comfortable assuming the original transom drain tube is immune to electrolysis as I understand it began life as brass and it's sure as hell copper-colored now - a sure sign of electrolysis in cast brass or bronze props, rudder fittings, keel-coolers, shaft struts, thru-hulls, etc., with which I'm familiar.

My boat does not have 115v AC aboard so that's not a factor. The batteries are solar charged at the dock, adequate when the boat's used every couple weeks. (With the boat on the hard for now, the batteries are in my garage, a Battery Tender rotated among them.)

One would hope galvanizing on our new steel pilings would offer some protection from making our harbor hotter, at least while the zinc lasts, but that seems not the case. Our docks are fairly new; AC wires supposedly run in chases well above the water and we residents patrol for visiting power cords in the drink. With the new pilings came accelerated galvanic action, not much question about it. The Port (owner of our harbor) was convinced enough to buy new propellers for a 70' twin-screw whale-watch boat here when its large bronze props went away alarmingly fast right after the new pilings went in. The boat's owner last week told me the new wheels are in trouble again, just a couple years later. He's had an impressed current system installed and crosses his fingers. Tough battle.

 

[thataway]

Even though the dock is properly wired--and one would have to assume that it is being done by the county....but..one never knows it only takes one ground tied to a neutral on the dock. The major point of issue, is individual boats. A large number of them, are not properly wired, with isolation from shore ground, with a galvanic isolator. (Especially old boats). It is also amazing how often one finds a boat with neutral and hot reversed--and in this case it is not unusual to find a very high (enough to shock or in some instances kill).

In the Large power cruiser--one would hope that the owner, and the dock master had the boat carefully checked--as well as the docks. I have seen 'inspected" docks miss wired.

Yes, the pump under the "step" of starboard pumps out the area of the cockpit when the boat is sitting in the water (normally does not have to be trimmed bow down--but, it doesn't take much water in the cockpit to make the stern pump also functional.

No, the pump in the cabin will not pump out the floor of the cabin. I found this out several times this summer. Apparently my vent tube or fill for the water tank in the 22 has a leak, and I got water on the cabin floor when filling up the water tank. This is another use for the plastic piston pump.

Interesting that your 2006 (05?--no HIN in your profile) has the glass door.
My 2006 (Dec 05 manufacture date) has the starboard door, with opening window--and I know of other 2006 which also have the glass door)--I can assure you that I have never seen one of these glass doors which was watertight !

Just after I sold the Cal 46, but still at my dock, with the new owner aboard, there was a lightning strike on a nearby power boat, with a lobe which took out the diode on the main engine regulator, and thus the 30 amp battery charger was feeding full power into the ground system on the boat. Ate up prop shaft, 26" prop, rudder shaft, and most thru hulls in about 2 weeks! (I was in S. Florida buying a trawler--and found the problem in about 1 minute (put my hand on the alternator, which was hot). So there are lots of things which can cause electrolysis! (in this case DC current)

 

[hughpenk]

Brooks and Judy mention solar panels charge the batteries, could galvanic actions be caused by the boats solar generated electric? On my boat I have suspected problems generated by 200 watts solar that powers up my refrigeration.