MerCruiser 350 MAG EFI - idle issues

I have a 2004 centurion elite v with a MerCruiser 350 MAG EFI that is slow to start and when it does, the idle is around 500, even when cold. is this controlled by the IAC valve? seems like it should idle a bit higher to start and then idle down after warming up.

Anything else I should look into? I am unsure how idle is controlled otherwise.

thanks!

Edit, I believe the previous owner replaced with a less expensive non-mercruiser part (automotive, not marine grade). not sure if that is pertinent but thought I would throw it out there.