Replacing Anodes

[lampshuk]

Hi, all. We bought a Moody 31 last November. Our first episode of boat ownership, so doing some routine maintenance jobs for the first time.

The pear-shaped hull anode needs replacing. I sprayed the external nut liberally with freeing oil but it refuses to budge - though the whole stud turns quite happily in the hole :-( - it was only after doing this and trying unsuccessfully to hold the interior nuts that I noticed a flat retaining "washer" on the outside that ought to be able to hold the stud steady. It's hard to get a proper spanner on it, though.

I suppose that, having spun the stud around, I will now have to draw it out and re-seal it.

But before that, I need to get the flippin' nut off the outside. Anyone got any strategies that work? I am slightly nervous of applying heat, given the proximity of the hull.

The studs seem to be made of mild steel. They have not rusted badly, but enough, it seems, to sieze on to the nut. Is there a better material to use for the stud? I have seen stainless steel ones on sale, but I thought their conductivity was poor. I suppose nyloc nuts won't work if the nuts provide some of the electrical connection.

Any tips for how best to proceed? I suppose this ought to be a simple, routine task, but as with all things nautical it seems that there are many "inconvenient details" that need to be worked through.

Thanks for any advice,

Lampsh.

 

[VicS]

You should be able to remove the outer nuts while an assistant holds the inner ones.

I suggest if its all rusted up you cut the old ones off and replace the whole stud assemblies along with the new anodes ... dont forget the backing sheet between the anode and the hull.

Studs are usually zinc plated steel. The anode will protect them while immersed and the zinc plating will help to stop them rusting when out of the water.

Stainless steel fixings are available if you require.......look nice on mobos stored on racks when not in use.

See the MGDuff website , esp the section on fitting anodes. http://www.mgduff.co.uk/

Check the bonding to the parts being protected when you have fitted the new anodes



Since you mention it a typical resistivity of mild steel is 17 x 10^-8Ωm while that of 18/8 stainless steel is 66 x 10^-8Ωm. So yes stainless steel has a much higher resistivity but I will leave you to work out the actual resistances of studs made from both materials and to decide if they are significant but I think you will find they are not and in fact small compared with the resistance of the recommeded 4mm² bonding cable.

 

[alahol2]

If I were you I would remove the inner nuts and withdraw both studs and the anode. You should then be able to put the square nuts into a vice while you remove the outer nuts. Whatever happens you will need to re-seat/seal the studs now that you have turned them. If they clean up OK then there's no problem re-using them (no one will see the rust). If you replace them then stick with the plated mild steel ones. I usually put a smear of grease on them each year and it keeps the rust down to manageable proportions.

 

[SimonP85]

We've just tacked the same problem on our 346

External nuts would not move. Purchased a nut cracker off eBay (link below) which allowed us to successfully remove the nuts, however we then discovered the thread on the studs to be in a poor state (not due to the nut cracker!). Reluctant to remove the studs the next eBay purchase was a M10 thread die cutting kit which thankfully has left us with newly usable studs! £10 of tools and 30 minutes work.

Nut Cracker - http://www.ebay.co.uk/itm/321241394081?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

 

[MoodySabre]

Some Moodys had the square plate on the studs glassed in. Where possible it is better to fit new studs - not expensive. The MOA website has several accounts of people just cutting the glass off and taking the old studs out.

 

[lampshuk]

We've just tacked the same problem on our 346

External nuts would not move. Purchased a nut cracker off eBay (link below) which allowed us to successfully remove the nuts, however we then discovered the thread on the studs to be in a poor state (not due to the nut cracker!). Reluctant to remove the studs the next eBay purchase was a M10 thread die cutting kit which thankfully has left us with newly usable studs! £10 of tools and 30 minutes work.

Nut Cracker - http://www.ebay.co.uk/itm/321241394081?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Now that looks like a useful bit of kit to have in any case. Order placed! Even though I will have to re-seat the studs, I think it's going to be easier to get the nuts off sideways and just poke the studs in than unwinding all the bonding bits. I will check the resistance, though.

I note that you're supposed to replace the backing pad. Since I have not yet become acquainted with mine, can someone tell me what they're made of? I have some thin neoprene sheet and would like to use that if I can avoid another trip to chandlers.

 

[alahol2]

I note that you're supposed to replace the backing pad. Since I have not yet become acquainted with mine, can someone tell me what they're made of? I have some thin neoprene sheet and would like to use that if I can avoid another trip to chandlers.

Over the years I've had thin rubber sheet, neoprene and some sort of plastic foam. Your neoprene sheet should be fine.