Ray, it sounds like you had typical "new electronics new boat" trouble. A side note, my antique Garmin has no problem with rechargeable cells of any kind, but Chinese high capacity NiMh cells all seem to be built with bad technology, they will self-discharge and go dead in 3-4 weeks, versus 6-9 months for Panasonics from Japan. (Sooner or later one or both of those may change.) I just won't buy them anymore, I can't use them unless I know in advance when to start rotating batteries through a charger so they'll be fresh to go.
Spending twice as long to go one way as you did the other, sounds typical. Incredibly good time for that small boat and that course, sounds like there must be significant current that helped you back.