28 bertram bonding system questions

[megalodon4g63]

I have a 28 Bertram and was thinking of redoing the bonding system with the 8awg marine wire. I was curious about installing a transom aluminum bonding block (transom zinc) and was not sure on how to install this item. Does anyone have any suggestions? I've switched to using aluminum instead of zincs since it is considered a better option these days. I've also heard that I should not use stainless steel thru bolt, but consider using a bronze type bolt instead to mount the anode. Also wondering on what size to use. I do have 2 shaft aluminums on each prop shaft, and 1 on each trim tab. I will be drilling my rudders to take an anode each as well since they were never drilled. Could I get away with using a grouper anode instead and clamp that to the green bonding wire while I'm docked instead of installing the transom anode so I don't have to do any drilling? Lastly, I was considering on installing a shaft brush as well - does anyone have one of these installed? The reason why I want to make sure everything is bonded correctly is because I purchased new NIBRAL props and want to protect them as best as I can since they are so pricey. The props that originally came with the boat seem to have been victims to galvanic corrosion and are somewhat brittle. I DO NOT want that to happen to these. Considered a prop nut anode too, but I think I may be overdoing it at that point. I'm sure as I redo the bonding wires that I may have many other questions to follow. I appreciate any advice and thanks in advance.

[Joseph Fikentscher]

I don't think aluminum is for salt water. I would use zinc.

[Tooeez]

I put the oval transom zinc made for SeaRay on my 28 about 30 years ago. I bedded a 1 inch thick mahogany backing block on the inside, and used 1/2 ss carriage bolts to go through the block and transom, followed by a flat washer and nut. The anode mounts on the bolts (the nut up against the transom spaces it off the hull) with another nut holding it on. I ran a #10 wire from each bolt to the bonding strap mounted on the bilge stringer, port bolt to port side, stbd to stbd. Works great--the anode lasts about a year. You can get zincs from boatzincs.com much cheaper than any marine store.
One of the bolts holding the mounting plate for the rudder stuffing boxes should be connected to the bonding system. A wire should go from that bolt to the clamp bolt on the rudder tiller arm--that bonds the rudder to the system, so there is no need for a separate rudder anode.
Unless you have one of those rubber spacers for mis-alignment between the shaft and transmission there is no need for a shaft brush--the shaft is connected to the engine, and the engine is connected to the bonding system.
You must use zinc in salt water--aluminum is for fresh or brackish water.

[megalodon4g63]

I don't think aluminum is for salt water. I would use zinc.

Aluminum anodes, alternatively, offer several advantages. They’re immune to the calcareous coating menace and are therefore well suited for use in seawater, as well as brackish and fresh water. Aluminum anodes also pack more of a punch; they either last longer than zinc anodes of the same weight, or provide the same protection as zinc in a lighter package. Their relative energy capacity is 1,108 amp hours per pound (significantly more than zinc), with a voltage of negative 1,100 millivolts. If you opt for aluminum anodes, be sure that the change is universal for all anodes used within the same bonding system.

https://www.cruisingworld.com/how/zinc- ... des#page-2

Aluminium Points To Note

Used in salt and brackish water
High nominal electrical capacity – up to 3 times higher than that of the same mass of zinc, so you can protect more with less
Aluminium anodes stay active and also remain active if exposed to air, if zinc anodes are removed from water they coat over
Often less expensive than zinc
Aluminium anodes will reactivate when re-immersed
Lighter to ship and to fit
Can last longer so less frequent changes means less maintenance cost
Cadmium free
More and more anode parts becoming available as the benefits of aluminium become understood

https://www.anodeoutlet.co.uk/aluminium ... nc-anodes/

[Tony Meola]

The aluminum anode has become very popular. I find that they corrode faster than zinc.

Be careful because you can over anode a boat. On my 31 with nibral props I do not have a transom anode. I run two on each shaft and the R4's on each rudder.

If you have everything bonded correctly you should have no issues.

Galvanic corrosion can come from several places. Natural re-action of disimilar metals', a voltage leak from your boat or the boat next to you or from the marinas 110.

How long have had the boat and are you keeping it in a marina? What kind of shape were your anode in when you pulled the boat for the winter?

Before I would put a transom anode on the boat I would put two on each shaft and one on each rudder. Fix all the bonding. Do the thru hulls, the rudders, make sure it bonds into the common ground and the engine blocks.

Originally Bertram tied anything metal into the bonding system. Out riggers, rub rail etc. If you run the 110 add a galvanic isolator.

If you find you still have a problem then you need to figure out if it is your boat or something in the marina.

We had a problem one year and we were eating up zinc every two weeks. Turned out to be a bad bilge pump. Changed it and problem solved. It was easier for us since we keep the boat in a lagoon and not in a mnarina so we are not dealing with other boats being right next to us.

If you decide to put on a transom anode, I would not be afraid to use stainless bolts. Remember the aluminum anode sits on stainless shafts. Make a good backing plate, one that will not crush when you tighten the bolt and one that is fairly rot resistant. Then tie the bolts that hold the anode on into the bonding system.

If you make a wood backing plate I would give it a coat or two of fiberglass resin to make it water resistant.

After all this if the anode do not last a season, then you need to start the search for what is causing the issue. That is a whole other story.

For the bonding system you can either use a copper strap or 6 or 8 gauge wire.

[megalodon4g63]

Thanks for the replies. Yes I keep my boat in a crowded marina. My zincs looked normal last season and season before. 3 years ago though I also had a bad bilge pump which ate everything. The props I had always looked like victims of galvanic corrosion. Got them that way. I just want to be safe before I dunk these $1500 props in the water. I will hold off on the transom zinc, but I may dangle a grouper/fish anode over the transom and keep an eye on it to see if a transom zinc is even needed for next season. Between the double shaft zincs, rudder zincs, trim tab zincs, and anode on a wire (fish) I should and hope I will be fine. Btw, is it true that the AC ground bus and the DC ground bus should be tied into the bonding system? Green AC wire goes to AC ground bus which goes to bonding wire. If there is a short in AC system, doesn't that mean that it will travel to the engine block via busses and down the shaft and into the water and shock someone who just so happen to be dipping a crab net at the same time? Be my luck. See diagram below.

http://lambdarepos.org/boat-battery-wir ... g-diagram/

[Tony Meola]

You need a Galvanic Isolator on the AC Side. The Isolator goes between the 110 inlet and the AC Panel. The Green wire runs from the Isolator to the Block/Bonding system.


I have this one on my 31. The new requirements also require a ELCI be installed also. This is basically a special ground gault switch.

https://www.bing.com/search?q=masdealli ... lang=en-US

https://www.westmarine.com/WestAdvisor/ ... Protection

The DC panel should ground to the bonding system. In fact, the Blue Seas panel I put in had a spot for a ground wire to run from the panel to the Bonding system. Scroll down to the last page on the link below. You will see on the diagram the two points that they have for the ground to run to the bonding system

http://assets.bluesea.com/files/resourc ... s/6680.pdf


Hope this helps.

[megalodon4g63]

Thanks so much! I will post if I gave anymore questions. This site is awesome!