You know, this is probably of little use to anyone but the lake I live on is almost brackish. The upper lake is fresh, the lower lake is brackish and the middle lake (where I am) is somewhere in between dependant on how much its been raining - for real

. Thus my choice for anodes is just confusing for me.
However, I have come to discover with research that my jetboat used zinc from the factory (dealer could never tell me what they were made of only "what the factory sends 'em with"

).
OK, so it is a jet drive but the principal is the same - stainless fittings aluminum housing etc. Now that boat sat in the water and the zincs disintigrated as they should but the drive was absolutly flawless after 3 seasons - even on edges that had been bumped, scraped or just worn away thus exposing the aluminum. There was absolutly no sign of corrosion to be found BUT the drive was always completly submerged while in the water not trimmed up as I have seen some people with I/Os do. Could this have anything to do with it? Anodes have to be submerged to work right? I have had luck in the past with zinc in my area so I think I will ask the dealer to equip the same, or at least get a zinc kit.
planealternative I do hope you get some satisfaction the corrosion issues you and other Volvo owners are describing - it does seem quite excessive - like an issue with thier blend in housing material or poor finishing practice. Being another Canuk with a Volvo on the way I do hope we are going to see you get some form of product backing up here. After watching this and other threads like it I will certainly be inspecting mine often!