Removing old rusted in anode

[pcatterall]

The zinc anode on my boat is heavily coated and pitted. As we will be back in sea water next season I would like to replace it.
This is the through hull bolted type with two bolts through. inside there is a glassed in wooden pad and connections from the bolts ( one to the stern gear and one to the engine)
The bolts outside are badly rusted and I cannot turn them.
Can I just 'bray' the bolts out from the inside and then replace them with SS when I refit the anode.
I did try a tap or two from inside without success but thought I had better seek advice before getting the lump hammer out.
I am sure I have asked this question a year ago but a search on my name and anode reveals only a different question. Please bear with me on that!!
Many thanks

 

[bert49uk]

you should have something like this
if you cant undo the outer nut undo the inner and as long as the square is fitted correctly to the outer hull you should be able to knock out, very unusual not to be able to undo outer nut, most times they shear off

 

[rob2]

Just to be sure - the square sits on the outside of the hull to stop rotation. I'd be inclined to cut the outer nuts off so that the anode can be removed, then drive the studs out with firm, confident blows of the club hammer, there's no longer anything hanging on them so nothing to go off at an angle and jam them. Last time I replaced mine I used plenty of sealant but still found the wood block inside got damp. It swells with the damp and maintains a seal.

Rob.

 

[pcatterall]

Thanks for the advice. Job done. Took off the inside nuts and terminals. The first outside nut sheared off. I found that I could turn the square plate and the bolt sort of screwed out. same process with the other one. Just need to order two new bolts now ( and the anode of course!)
There is/was a rubber gasket on my old one, is this essential or is sealant ok?

 

[VicS]

There is/was a rubber gasket on my old one, is this essential or is sealant ok?

According to MG Duff

Whenever an anode is fitted to a GRP or wooden hull an anode backing sheet must be used to control the wastage of the anode and protect the hull. The anode backing sheet should be replaced each time the anode is replaced.​

RTFFI ( full fitting instructions) at http://www.mgduff.co.uk/leisure-craft/fitting-instructions/fitting-bonding.html