View of the internals.
First step is to draw the cutout (barely visible pencil line!). The bottom of the paneling is supported by a metal ledge that was the outboard support for the bus seats.
We drilled a guide hole in the upper left corner as a place to start the jig saw cut.
We cut the birch and insulation from the inside using the jigsaw. The outside cuts were made with the jigsaw and Sawzall.
The steel perforated rail was flattened to the outside to add support & cover the insulation.
It fits! But what about those rub rails? Time for some angle-grinder action.
With the rub rails trimmed -- perfect fit -- even allows for the brushed-aluminum cover.
Butyl tape was applied behind the flange and 3/4" self-drilling screws were used to fasten the heater to the bus body.
Inside view. All fo the connections are easily accessible -- incoming (cold) water, outgoing (hot) water, propane, and 12vdc positive and negative wires (uses 1 amp). When the counter unit is installed, the heater sits directly below the sink -- which means a *very* short run for the hot water.
Outside view with snazzy brushed aluminum cover. The lower louvered section is the air intake, the upper perforated section is the vent/exhaust.
3 windows and a water heater installed -- a productive weekend!