boat misfiring and now won't turn over

hey guys i have a 2000 supra launch with the indmar assault ....so today me and a few friends were out riding we all took our sets the boat was running awesome.. then we sat around for about thirty minutes and when i got out to take my next set the boat started and then when u tried to put it in gear it would just die.. so i hopped in and just tried to put rev the motor up and it would start and just act like it was trying to run then it would back fire a couple times bog down and die.. did this for a couple times and now she won't even fire up.. it will crank but no firing up.... temp was good oil pressure was good.. just filled up with fuel.. i thought it was vapor lock so tried the water on fuel pump no go... we got pulled in took about 1 hr tried again no go... there are so many possibilities with EFI motor.. i have never had to hook it up to a reader and wanted to know where the plug in is so if its a sensor i can change that... but any suggestions would be greatly appreciated i think i need to start at the fuel filter and spark plugs.. a bud said proxy bad gas... I'm lost as u can tell reading this .. please help!!