Thank you for your help, I think I may have narrowed down the problem but I am still getting some conflicting information from some sources !

I can confirm that the saildrive isolation gasket is in place and in good order, as are the isolation spacers on the bolts.

The corrosion of the brass plate covering the impeller was eveident prior to me buying the boat in January but to a much slower degree. The previous owner rarely used shorepower long term (Brighton Marina) and also confirmed that anodes were replaced annually which was sufficient.

The anodes were in very good order in January this year when the boat was surveyed.

I can see that my hull anode is directly bonded the gearbox side of the engine isolation gasket (bonded twice, once at each end of the anode) which according to the Volvo agent is incorrect, the boat has obviously been like this for some time, maybe explaining the corrosion, now accelerated by both the use of shorepower and Ocean Village marina which can be harsh on anodes according to other berth holders.

However Clipper Marine say they often see this bonding arrangement between gearbox and and hull anode but all the install manuals from Volvo say this is incorrect !!

I have looked at another Volvo 2020 saildrive in the marina (in a Maxi 1000) and this too has the bond on the gearbox side of the isolation gasket to the hull anode.

I would be very keen to hear from other BOA members who have a 2020 Saildrive as to whether the hull anode is bonded to the engine block or gearbox side of the isolation gasket.

As I say the Volvo agent is very clear that the bond should be between the engine block and hull anode, but it would appear that in practice this is not always the case.

Many thanks

B32 – Rigmarole