Posted: October 21 2010 at 13:00 | IP Logged

I own a 2003 330SE (Elegante) with twin Volvo Pentas.  Both outdrives have excessive surface corrosion, which includes peeling and chipping paint and pitting of the underlying metal.  No other through-hulls or external or internal metals show evidence of corrosion.  The boat has only been operated in fresh water since new. I owned a 2002 250SE (Monticello) that had the same problem but I never got around to troubleshooting it.  I suspect that possibly the boat has zinc anodes, which are intended for saltwater, as opposed to the magnesium anodes it should have for use in freshwater.  Could this be the cause?  How can I determine if my anodes are zinc or magnesium?  Is there a difference in resistance that I could check with a mulitmeter? Chip some off and see if it burns (an old navy survival vest I used to use included a bar of magnesium intended for this).  I do have a ZINC SAVER system, but I do not know if it is operating or operating properly, which I obviously need to look into as part of the troubleshooting process. Any ideas are much appreciated. 

Thank you,

Sean