How to fit new through-hull anode?

[gwingn]

I need to replace ( on a Westerly Griffon ) my main hull anode and mounting bolts, unfortunately a previous owner has fitted rather nice stainless fuel and water tanks above the existing fitting so replacing a sheared bolt would mean removing the complete engine and both tanks to get access. I think my best option is probably to re-site the replacement anode a bit into a position allowing maintenance and I have a set of bolts with electrical connectors for that purpose.

Can anyone advise how such anodes are normally fitted? Is the the hull normally just drilled and the bolts fitted with liberal use of sealant or is it usual to drill and tap the (solid grp) hull?

Regarding the old fitting, given that I cannot get access internally to remove the bolts I'm wondering what the best solution is here. I don't fancy trying to drive them out from outside, particularly if they are tapped in, as there may not be sufficient headroom between bolt head and water tank to do so. One idea is to simply grind them off flush with the hull and then fair them in with a good lump of epoxy, another would be to use a hole saw to cut around both bolt and nut so as to remove them completely from the outside and then plug the holes - that seems wantonly destructive and a bit frightening to put largish holes in the hull.

 

[VicS]

This video might answer your questions regarding fitting a new anode but google "how to fit a hull anode" and you will find more

Repairing even a small hole properly can develop into a much bigger job than you'd expect especially with access from outside only. The West resins site has loads of information

Instruction | WEST SYSTEM Epoxy

.

 

[alahol2]

Why do you feel the need to replace the mounting bolts? Mine are probably 20+ years old by now and they tend to get rusty but I can still undo the nuts without disturbing the bolts. I replace the anode every couple of years with an interim chip off and clean up in the intervening winter.

 

[Tranona]

Do you have a shaft anode? If so the hull anode is klikely doing very little

 

[gwingn]

Why do you feel the need to replace the mounting bolts? Mine are probably 20+ years old by now and they tend to get rusty but I can still undo the nuts without disturbing the bolts. I replace the anode every couple of years with an interim chip off and clean up in the intervening winter.

One has sheared off when removing the old heavily corroded nuts, I would replace just that one bolt if it was somewhere accessible - but it isn't.

Do you have a shaft anode? If so the hull anode is klikely doing very little

Yes I do, but the large hull anode seems to be doing much more of the work than the small one on the shaft - which isn't corroded away anywhere near as much. The hull anode is I understand necessary for the heat exchanger.

 

[gwingn]

This video might answer your questions regarding fitting a new anode but google "how to fit a hull anode" and you will find more

Repairing even a small hole properly can develop into a much bigger job than you'd expect especially with access from outside only. The West resins site has loads of information

Instruction | WEST SYSTEM Epoxy

.

Thanks, that was helpful. In that video they didn't tap the holes but instead just drilled them wide enough to push the bolt through and then relied on sealant.

 

[Tranona]

One has sheared off when removing the old heavily corroded nuts, I would replace just that one bolt if it was somewhere accessible - but it isn't.

Yes I do, but the large hull anode seems to be doing much more of the work than the small one on the shaft - which isn't corroded away anywhere near as much. The hull anode is I understand necessary for the heat exchanger.

No It does nothing to the heat exchanger which may or may not have its own anode. The seawater in the heat exchanger is essentially isolated from the outside seawater. Galvanic action occurs when the 2 metals are in the electrolyte in sight of each other. so a heat exchanger will have the node inside where the 2 metals are. Likewise the shaft anode is electrically connected to the shaft/propeller close to the propeller it is protecting so will go first. If it is not then possibly not a good contact. What is the hull anode connected to?

 

[alahol2]

Amazingly that video appears not to mention the internal nuts apart from a diagram.

Please don't "push the bolt through and then relied on sealant" ,

Push the bolt through with sealant and get nuts and washers tightened up.

 

[VicS]

Amazingly that video appears not to mention the internal nuts apart from a diagram.

Please don't "push the bolt through and then relied on sealant" ,

Push the bolt through with sealant and get nuts and washers tightened up.

Yes I spotted that but I've posted the link several times and so far you are the only person to have commented on it.. Perhaps you are the only one who has viewed it

.

 

[gwingn]

Yes I spotted that but I've posted the link several times and so far you are the only person to have commented on it.. Perhaps you are the only one who has viewed it

.

Viewed but I sort of assumed that it was obvious you had to fasten the bolts on both sides of the hull. How the replacement kit come pre-assembled is a bit of a clue

 

[gwingn]

No It does nothing to the heat exchanger which may or may not have its own anode. The seawater in the heat exchanger is essentially isolated from the outside seawater. Galvanic action occurs when the 2 metals are in the electrolyte in sight of each other. so a heat exchanger will have the node inside where the 2 metals are. Likewise the shaft anode is electrically connected to the shaft/propeller close to the propeller it is protecting so will go first. If it is not then possibly not a good contact. What is the hull anode connected to?

It is connected to the engine. There may also be a second connection to something else but I'm going to have to get an inspection camera down there to see if that is the case.

 

[Tranona]

The normal connection is to the gearbox/engine connection which usually gives a path to the shaft. However if you have a flexible coupling you need to have a bridge. to check if it is actually doing any good carry out a continuity test between the propeller and the anode.