2003 496HOs came out of no wake zone, tried to take off but once I hit around 3000rpm I got a constant beep in the starboard engine. Came to a stop, let it idle for a few seconds but the alarm kept going until I turned off the key.

Started it back up, revved it in neutral sounded fine, put it in gear and the same thing happened. I tried putting it in neutral and revving it while the alarm was going off, but it would not rev. It would kinda stumble off idle to maybe 900rpm. So shut it off again and did that same thing about 4 times.

Any ideas??

I have a different model/year/make but a lot of stuff is the same. On mine I'll get a warning if:
Oil press too low
Water temp too high
Drive lube bottle low (or internal sensor is bad)

Verify drive lube bottle is full. If still alarming, try disconnecting wires to drive lube bottle level sensor.

yeah, drive fluid was full. I ended up buying a scan tool so hopefully it'll be something simple like a sensor.

Scan it. The codes will give you direction on what it is.

I had something similar happen and it was the water pressure sensor wiring(corrosion in the plug). Replaced the connector and it was good to go.