We surf year round and this past winter, my 11 year old grand daughter starting going out with us on cold days.
We were on my buddy's boat in December and he had a heater.... when Taya wasn't surfing, she was bundled up and had that tube inserted in the bundle.
me being the fat F that I am had always relied on the walrus effect for heat.
well, I broke down and ordered a 3 port 42,000btu unit from heatcraft up in Idaho.
when the unit came, I laid everything out and saw that I hadn't ordered a circ pump.
theirs was pretty pricey so I got one on Amazon for $70.
it met the specs of heatcrafts but was built for solar hot water. It works fine on 12 volts.
i mounted the unit by drilling and bolting it to the rear seat framing just above the vdrive. I ran a tube and vent to cockpit area.
i also ran a tube to stud and port sides. I didn't want to drill the seat bases and take up storage and speaker room. So I ordered ABS sheet- 3/16 thick and drilled 2 tube ports. I made one for each side and put them in place of the trays ( that seem to collect garbage) between the cup holders. I put a y on each duct and made new tube holders out of 3" abs pipe.
so I have 4- 6' tubes. 2 per side plus the driver vent.
I ran the hoses to the marked fittings on the engine.next, I ran the wire to the existing heater switch. I tied the pump power into the fan power.
I believe that this project was worthwhile for what we do and was well worth the money.