240V in the US is NOT 3 phase. 3 phase has 3 hot wires, with each wire exactly 120 degrees out of phase of the other two. It also typicaly has a ground, and a neutral. It is very unusual to find a 3 phase generator on a boat. Typicaly the only reason to have 3 phase current
is with VERY large electric
240V in the US has only 2 hot wires. They are both hot, but have the voltage 180 degrees out of phase with each other, so that the differental is 240 volts. It also typicaly has a neutral.
According to the following website, the Westerbeke 7.6 EDT D-NET 7.5 is wired to provide 120 and 240 V US style current
. It might already be wired into the boats wireing system, and just require the proper breakers and wireing in the boats main breaker box.
I can't find a specification for dive compressor. Depending on the specs, it might be quite easy. There are apperently 3 phase version, which would be very difficult to wire in. There are single phase 240V versions that might be quite easy, and 120V versions. Depending on which one you have, it could be easy, or hard.