Anodes - gh26

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JFJ
Posts: 24
Joined: Tue September 6th, 2016, 12:07 am

Anodes - gh26

Post by JFJ »

Hi all

I had the steel keels of Iris shot blasted, and refinished in 3 coats of 'Jutonmastic 90' - an epoxy 2 pack marine primer. Looks a great job - havent antifouled yet.
The previous zinc anodes did a great job on these wings - there were 2 bolted through each, with the metal cleaned in direct contact and I didnt have much pitting - indeed, most of the original galvanization was still in place.

However, now I have epoxied the surface, I am not so keen on cutting it back round the anode.

I have some old 'Arc' copper multiply welding wires from a heavy duty machine - heavily lugged and each about 15 ft log, and perhaps 8mm thick. I was thinking of bolting these to the keels on the inside, and running them back to a large anode fitted in the stern. Good idea - or should I grind the epoxy?

On a second note. The aft anode (a double bolted affair) had 2 wires comming off it. One is attached to the engine bell housing (and looks like a diy job fitted later), while the other had broken off completely and I dont know where it went! The whole wire was in the bilge. Now, the engine is a volvo penta MD 2020, in good shape. According to my reading of the workshop manual, the engine should be 'galvanically isolated - they are not to be connected to an anode. The drive shaft has a plastic thrust coupling, and the alternator and starter have direct negative connections - so I can see that it could be so. The stern gland was replaced before I bought the boat. The question would be then - should the anode be connected to the stern bronze drive flange - and then - what about the prop - it would usually be isolated with the rubber in the cutlass bearing. There is no anode on the driveshaft....
JFJ
Posts: 24
Joined: Tue September 6th, 2016, 12:07 am

Re: Anodes - gh26

Post by JFJ »

Well,
I got my hands on a copy of 'boat owner's Mechanical and Electrical Manual' by Calder.

Seems I went overboard on the cables - only need AWG 8. so important because the wire I have is expensive stuff and would be better off with other projects - pain to re-crimp too!

As to the bilgteplate anodes - I think I will grind a patch through the epoxy - it is the best protection in the event of a grounding affecting the bottom edge.

As to the 'main' anode. It appears that it was 'oversizesd' - this is a bad thing - as it seems to have affected the surfacce of the gelcoat through alkali damage... I had wondered about that when I recoated with barrier coat. It appears that at some time, the zinc basically disolved in place, and released its hydrogen into the gelcoat - blistering it a bit. Seems (according to Calder) to be due to either an oversized anode or an anode which isnt bonding. (which would explain the original wire which is broken and I dont know where it went.) I think that going forward (I will refit the existing anode - still a KG left at least) I will connect the wire to the sterngland -but will assess at the weekend.No way I think that can protect the prop though.
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