Low tech skin fitting bonding

[Mudhook]

Hi folks.

Having just pulled the engine out of my 30-year-old fibreglass hull, I note that the only bonding fitted to any of the skin fittings is a pair of cables from fore and aft legs of the engine mounting to fore and aft bolts of the external anode. Is this all I need?

There are several hull seacocks for engine, heads, etc, and none are connected by wires, but all are in good condition and there's no apparent corrosion on any of these or the prop. I don't have shore power and some books (notable Alastair Garrod's Electrics Afloat) seem to think that galvanic problems are minimal when shore power is not present.

Can the wise men advise?

Regards, Mudhook.



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[DMGibson]

Nothing seems to be broken, so why change it?



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[MainlySteam]

If the skin fittings, propellor, etc have survived for years with no problem then that is indicative of correct materials being selected in the first place, those being ones that are quite happy in salt water without protection. As DMGibson says, if all is well do not change it. I would add that bonding currently unbonded but happy items or adding more zinc may introduce problems and I would personally avoid doing so.

Despite the tendency of many to want to turn their boats into batteries by wiring everything together with zinc anodes, it is actually easy to build fibreglass boats with suitable choice of equipment (eg no saildrive) and correct materials such that anodic protection of any sort is unecessary except one anode for use as a convenient point for an ac ground if ac power is installed. This is also possible with steel boats and as an example of that we have just lifted our own 7-1/2 year old steel yacht, which only comes out of the water for 2-3 days every 2 years, and there is no evidence of galvanic or any other corrosion anywhere even though there is only one small anode on or in the whole boat (a teardrop on one side of the fin keel).

John

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