I put new anodes on my 1983 37 ft double cabin 2 years ago. I could never get more than about .7, even though John said I had more anodes than required. I was concerned but did nothing about it. I am now doing "The Loop" or was.( Currently held up at Atlantic Yacht Basin, just South of Cheasapeake Bay) When I hit salt water meter went to 0.9 & to 1+ at times. If you have 0.6 in fresh water you are fine, installing more anodes is a waste of $$.
Roger
Sea Jay
1983 37 double cabin, twin 230hp Volvo diesels, twin disk 1.5-1 20X 23 4 blade props