bertram31.com

I stumbled on this. I thought some might be interested:


http://www.martyranodes.com/sites/defau ... Anodes.pdf

Yannis

Interesting article. Here is the question, I have never seen engine zincs in aluminum. If you use Zinc engine plugs and aluminum on the shafts is that considered mixing.

Tony,
Good question. I'll have to ask my Yanmar guy what the 5+5 engine plug anodes are made off, as well as the rest of them on shafts, rudders etc.
I would tend to believe that what you are suggesting is mixing alright, isn't the boat a "single unit" when it comes to galvanic corrosion? Do stray currents differentiate between engine and shaft metals? Beats me !!

Yannis it will be interesting

Guy's,
The aluminum anodes are being used on the large out board engines such as Yamaha and Mercury. If the tree huggers in CA have there way we won't be able to buy zinc anodes in the near future. If you need zinc's buy only the good quality Camp zincs, the others are not worth buying.
Pete Fallon

Pete,first, I wish you well for your knee.
What if we purchased aluminum for everything; engine and shafts etc (for those at sea)? You mean to say too that there aren't but zinc anodes for the motors?
Another thing to deal with !

Yannis,
If your bonding system is still intact and all the drops are connected to the copper strips that are glassed into your stringers, I would stick with the original zinc anodes, use the factory Yanmar zincs for the engine and Camp zincs for your shafts, rudders, transom and trim tabs. My 1961 31 express has just 2 shaft zincs on the outside of the hull that's it. I have never seen the set-up that I have, when I bought my boat 36 years ago it had 2-3"x 6" zinc anodes screwed to the shaft backing plates on the interior of the hull, I changed them for the first time last year, they are connected to the copper strip on the stringers. I have never had a problem with galvanic corrosion since I have owned the boat,
I did have a problem at the Riviera Beach Marina years ago, it turned out to be a 120 volt line that was in contact with a piece of rebar that was hanging down from under the finger pier on the starboard side of my boat. The 120 volt line had chaffed thru the outer vinyl jacket and made contact with the rebar, the live wire was introducing 120 volts directly into the water and it ate holes into my starboard prop. When I notified the dock master they fixed the problem and I never had another problem for the next 3 years. When the boat was in Massachusetts on a mooring behind my house I never had a problem and when I moved to South Florida Yachts wet slip I never had a problem.
The major culprit with boats having corrosion issues in a marina is usually another boat nearby that is introducing electricity into the water and it could be 12 volt as well as 110 volt stray current corrosion, more than likely a sailboat or a live aboard that has a lot of big box store bought appliances that are not connected properly.
A lot of boats have un-grounded appliances such as refrigerators, ice makers, air conditioners, I have seen a household style 3.2cubic foot fridge with the green ground wire that was not connected to anything, just laying in the bilge, the boat could not keep zincs for more than 2 months, after connecting the ground wire the problem went away.
I also have a Dyna Plate (gold beaded bar 4"x9") that is used for an earth ground for the old Loran A set that was on the boat when I bought it. Right now the only thing have on it is the ground strap(Stainless steel braid for the GPS earth ground).
If your having a problem with thru hulls, rudders, shafts and trim tabs corroding I would hire a marine electrical technician that knows how to use a Corrosion Meter to check if your boat is under protected or even over protected which can lead to metal failures.
The 240 Yanmars have a bunch of anodes all over the engines see your owners manual for location, I think there are about 6 to 8 for each engine, Yanmar uses a lot of dissimilar metals on the engines so pay attention to the zincs or you will end up with major repairs if you don't keep up with the zinc maintenance schedule. Bruce knows those engines like the back of his hand, maybe he will speak up about the zinc questions.
Pete Fallon

pete your right threre are 6 on my 230

Pete thank you.
If the stray current in the water were 230V instead of 110V, would the corrosion be faster?

Charlie, why do I keep counting my anodes and stop at 5? Do I miss one, or are there two Yanmar 240 models?

Yannis,
All I know is it can be a shocking experience, whether it's 120 volts or a million volts, you don't want anything with electricity to come in contact with unprotected metals on a boat. The old fashioned marinas were the worst culprits when it came to bad wiring, the electric supply lines were usually fastened to the bottom of the docks with steel wire staples, they failed within a year and ended up in the drink, plastic conduit wire chases are fairly recent additions and I've seen wire nut connections submerged in sea water, not even a lick of electrical tape on the joint and 150 foot runs without any circuit breakers anywhere in the line, it went directly into the transformer box at the top of the yard no breakers on the transformer.
I was at the Ft Lauderdale boat show a few years ago and was watching a 220 volt line submerged at the transom of a large triple outboard center console just bubbling away along with the lower units of the 250 Yamaha outboards and the stainless steel $600.00 props looked like Alka Selzer tablets.
Just keep electricity away from water and be careful where you dock your boat.
Pete Fallon

Pete, thanks and good luck !