Just bought a 24 commander it has a procharger 496 non ho. the rev limiter is stock at 4800 boat will run 5000 rpm so my question how does the rev limiter work on this motor should it cut out or alram etc. I am thinking if I can run to 5000 rpm maybe it has been reprogramed to a higher rpm

The factory stock rev-limit on a 496Mag engine is 4950rpms on soft limit and 5000 rpms on hard rev-limit so based on dash mounted tach gauge at speed its very reasonable for you to see 5000rpms on the tach before the engine rev-limit kicks in.
Taking stock Merc 496 engines beyond the 5100 rpm limit in a performance boat engine with stock valve springs and valve train is a real risky proposition and we don't do it.
It will not go beyond that unless someone has Whipple's stage 1 or 2 re-program and you can determine that by turning over the ECM and see if Whipple's programming file number is on the back of the ECM. At Raylar we do not reprogram stock engine 496Mag ECM's for higher than 5100 rpms and we do not reprogram for use with Pro Chargers at this time since we have no data input to develop a new program for this supercharger.

Best Regards,
Ray @ Raylar