I'll apologize now for my photo and caption on the soon to be published
photo of your retrofit!
My take on your masthead dome is that it really is a large Minni-Kota
at the top of your mast with a long-shaft drive down the center of the
mast to a retractable prop hidden in your centerboard trunk - which
explains why you were moving while others were only thinking about
moving. Maybe other readers comment on what THEY think it is! Bill?
Geoff?
Larry@Monterey
YUUKI HMS 18 #35