Don't be embarrassed by the question...You're actually smarter than the "average bear." Most people jump the conclusion that bilge
pumps are running full time on those boats and that owners need to know about it before their boats sink!
They aren't heat exchangers...What you're seeing is the HVAC
(central heat & air conditioning) system pump
, which typically are reverse cycle heat pumps. Boat
owners who use their boats year round leave heat running during the winter
to protect against freezing by keeping the boat
warm...in the summer they leave air conditioning
running full time to reduce humidity and the molds etc that humidity can cause.