Trojan Boat Forum

Need a little advice--- going to instal anodes on the rudders as they do not have any ,is there a preferred spot to place them on the rudders--thanks Mike

Here is where mine are. I think there is a hole on the rudder that the zinc bolt goes though.

Thanks for the pic SS--- that seems to be where it is the flattest---- looks like they will be going there---Mike

Are the metal fittings on your boat bonded? If so, there may be no need to zinc your rudders unless a reference anode shows you are under-zinced.

obeejr wrote:Are the metal fittings on your boat bonded? If so, there may be no need to zinc your rudders unless a reference anode shows you are under-zinced.

I will have to check that as I am not totally familiar with this boat yet----bonding was an option.One question---- what is a reference anode? The zincs that I removed from the prop shafts ( shafts look brand new) are zinc and did not look very worn ,but I am hearing that magnesium is preferred for fresh water.The only thing on the rudders is some oxidation so I just want to err on the safe side------Thanks Mike

what is a reference anode?

Read up on them here:
http://www.boatzincs.com/corrosion-refe ... trode.html Might consider finding a buddy or two and doing a local group buy.

And another useful website while I at it:

http://www.pbase.com/mainecruising/boat_projects

A reference electrode is a probe used to measure stray currents in an electolyte, or water in our case. While it's good to know the conditions in your own slip as this is likely where the vessel spends most of its time, we can't forget that a trip to another port with a severe stray current problem even for just a few days can cause major damage. Hense I always recommend as much cathodic protection as practical. A good marina will have the proper gear to take these measurements, and should be doing so at the start of every season.

The zinc anodes that are in great shape in our waters typically mean that they simply aren't doing thier job; not "sacrificing" themselves if you will, so ya, they last a long time in our waters. Given that it's likely there will be stray current no matter where you are/go, an anode that has to be replaced indicates that it's working. When you switch to magnesium, you will need to replace them every year not only because of wear but they will gain a coating that renders them useless if left on for too long. I suspect though that it will be obvious by the amount of deterioration after one season that they will need replacing before that point. When you change to magnesium, I recommend you convince/educate your neighbouring boaters to do the same otherwise your boat will act as one big anode in reffence to the boats around you causing your anodes to give up their mass at a much faster rate. This is often seen when a vessel on one side of you is well protected but the one on the other side isn't. Your anodes on the other side will typically be much more deteriorated than the side next to the properly protected vessel. Of course the guy with the wrong anodes will simply say "but my zinc anodes are just fine." Again, this is simply not knowing the science. Sacraficial anodes are just that; they are made to deteriorate in order to provide cathodic protection.

BigD thanks for that-------I think that I will just put the magnesium anodes on the shafts and keep an eye on them as the season progresses .If we check with the marina owner about the cathodic protection there we can draw a better conclusion, nobody seems to carry the magnesium rudder anodes anyway, it is all zinc.I have more time anyway as it seems I have to repair keel bleeding and deal with the hollow keel thing----Mike

Mag rudder anodes are readily available. Any marine dealer or marina should have no problem getting them or they just aren't dealing with the right suppliers.

Strange the marina(s) in your area don't carry the right type of anode . I would put 2 on each shaft . as the is a good chance other boater maybe using the wrong type. ans don't mix the type of anodes you are using .


http://www.martyranodes.com/content/mar ... es/Mag.php


If you use the search on that page it show places in your area you can get them .

I agree with both of you----- one supplier who I got the mag anodes for the shafts from told me,that to order could take up to 8 wks to come from china( those are martyr)--- I will check up north closer to boat---Mike

Boatzincs.com has plenty of stuff. I just ordered a full set of aluminum zincs.

China? there is a distributor close to you; Paynes.