To all who offered assistance thank you. Finding out intricacies about yacht is a giant and continual learning curve. Re water pump issue. After tracing wires, inspecting connections was ready to give up and remove pump but noticed power wires from pump top covering in protective plastic sleeve disappearing under HWS. Removed sleeve to find two joiners coated in clear'ish hard substance, I presume to aid waterproofing. Removed coating to find one crimp connector loose although not visible with the naked eye. Moving wire had pump spring to life. Obviously been there since production and for some reason decided to fail 6 years later. One nip with pliers did the trick.....thank goodness. New rule...don't trust connectors even if they look A1. Again, thank you for everyone's help.