It turns out the problem was carbon buildup on the brushes. We have put 20k nm and I am guessing the previous owners logged at least 10k nm on the unit.

Anyone have any luck finding replacement brushes for Raymarine Type 2 linear drive?

My understanding is that the brushes are: Morganite Electrical Carbon 6x10x20mm, grade CM9/M50-5113.  Or for those on imperial...0.24x0.39x0.79inches. I believe that's for the 12v model, but perhaps the brushes are the same? 
--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com