On a 2000 Scarab Sport 302 there are 2 fuel fills. Does this mean it has one tank for each motor or a main / aux tank set up?
If it is the latter, how do you switch between tanks?

Only 1 main tank , the other is an optional 50 gallon aux tank that is just in front of the cabin door , they are connected by a small crossover type hose that's why you have 2 fuel fills .... At least this is how mine are set up

X 2

Is there a valve to turn or does it just automatically feed into the main tank?

I am not sure , the only valves I have are on the main tank , buy check you hand homes in tbd deck to see if you have any inline valves for that aux tank . My guess is that it just automatically feeds to ybe main tank

Sorry, I can't help you. Mine has only 1 tank, as far as I know.

in my 2000 302 the front tank is the main tank, the rear tank is oval and is located just in front of the door to the battery and oil tanks compartment (rear) in the very back of the boat were your batteries are, there is a main stringer, on the left of the stringer there is a bracket that has two 2-way valves, if you follow your hoses it clearly shows you front, rear tanks to port - starboard engines. you can sellect any combination you want.
Nelson
the front fuel fill to front tank,, rear fill to rear tank,, your gauges top=front bottom=rear