need help!! 2004 rxp no beep no crank

[shannon]

I have a 2004 rxp that will not beep when the key is plugged in and it will not crank over but the guages come on and the trim works. It all started in the gulf 3 months ago when I flipped it. I rode it back to the ramp before I realized it had water in it. I drained the oil, filled it with new and ran it for a few minutes then changed the filter and oil again because the first change was a little milky still. We went out in the bay and rode for about an hour and all was good then to the gulf for about 30 minutes. I was jumping the waves as they were coming in and turned around for another jump and it died. I tried starting it and it cranked a few times then nothing. everything was still on but it would not crank so I removed the key and put in back on but still the same thing. Had it towed to the ramp and pulled it home to troubleshoot. I checked all fuses, even ohmed them to be sure and every one was good. Ohmed the starter switch, good.Jumped the soleniod and it cranked normal but did not start. Checked for corrosion on batt and ground on engine, none. I even swapped my mpem and ecu into my buddys 04 rxp which is exactly the same as mine and it worked like it should. I tried my spare key and my training key but same thing happens. Load tested the batt, good. Pressed the set switch 5 times to check the codes but no fault codes found. I checked all wires, connectors and pins and they all seem to be good.Beeper works when checking codes.At my wits end and ready to toss it off a cliff.Any advice, info, suggestions? please help!!!!!!!