heater on my 2002 B473 is an Attwood, 12 inch square cube. I had no issues taking it out through the port cabin
I had to relocate the water heater when I installed a Northern Lights
5 kw genset center line in the port rear cabin. Lowered it through the starboard lazerette and slide it through a hole we cut in the bulkhead. Very pleased and there is still plenty of room in the cabin.
My intent was to move the water water into the port rear lazerette however the opening is only 13.5 inches wide so I bought a long narrow heater that just fit. It is made by Torrid and is a thermos bottle design so it should be more efficient.
s/v Linda Marie