Advice on Anodes - Boat Slipped on Delaware River in Philadelphia

[lawndoctor]

To anyone who keeps their boat in a slip on the Delaware River in Philadelphia, do you have advice/experience on whether to use magnesium or alumnium anodes on a Bravo III?

I had severe galvanic corrosion for the first time last year, probably due to hitting flotsam and damaging the Mercathode unit on the outdrive, so we replaced the Mercathode unit this winter and just tested it to confirm it is working (also replaced the bearing carrier, which was all eaten up). But another thing that may have been different last year was I think the new yard (different than the one where I did winter storage in previous years) may have installed aluminum instead of magnesium anodes (their parts list on the bill last year did not specify).

This year, I told them to put magnesium on, but I just got the bill in the mail and the parts list says alumnium. I am considering taking the boat back to them and making them haul it and switch the anodes to magnesium.

What do people use on this stretch of the Delaware, and in particular does anyone in this specific area have experience switching between the two materials and seeing any different results from it?

Thanks very much for your help.

 

[larrytbull]

i think bravo ii uses aluminum in delaware, I used aluminum last 2 years on delaware river was in neshaminy state marina north of philly, I have inboards so may be different for bravo iii
but aluminum did just fine

 

[mwph]

This chart should be of help...

http://www.boatzincs.com/mercruiser-zinc.html

 

[lawndoctor]

Thanks for the responses guys. Turns out they put magnesium anodes on and the paperwork was wrong. Hopefully that and the replacement of the Mercathode will do the trick.