I have two outdrives that corroded over four months. The gardiennage company left my shorepower connected with all appliances switched on. Is it normal to leave the power on when there's no one onboard?
No it isn't usual to leave everything on at all. But I doubt it's caused the outdrive problem. If you want professional advice (foc on the 'phone), try calling Chris Harris of M G Duff - corrosion and anode specialists - extremely helpful - 01243 53 33 36.
I had the same problem a couple of years ago! I had both drives completely serviced with all new rubber parts and new stainless steel clips retaining boots. All new anodes were also fitted. Within four months all anodes had gone and the new stainless steel circlips had disappeared and water had entered the drive shafts doing lots of damage! I felt it was due to electricity leakage from pontoons, but couldnt prove anything at all. I did however make a claim on my insurance as I could prove that I had all this work done prior to the boat being returned to the water and they paid out after a lot of "looking into the problem"
Good luck