Back in December, James and Jennifer Hamilton, the globe-circling, high-tech cruising couple from Seattle, passed the 9,500-hour mark on the single 265-hp John Deere engine that drives their Nordhavn 52. That was in the North Atlantic. Since then they cruised to Ireland and then England, where, starting on Jan. 9, they decided to replace the cutlass bearings on the rudder shaft and on the wing and main prop shafts as well. They were at Saxon Wharf in Southampton. Hamilton gives a blow-by-blow account of what happened next, with pictures, all on their website (mvdirona.com). Here’s the short version: They loosened…