The old makos I know of may have a floating draft of about 1.5'... but most of them have a running draft with the skeg down of a good bit more than that. Plus, similar to what others have said... if you have to shut down that mako... there's a good chance you'd have to idle out... IF you can. Probably won't get it back on plane.
Use either the San Luis pass county park or Run up the ICW to the West intrance of Bastrop Bay... run it's channels which are deep. Christmas isn't too bad as long as you stay off the shoals that are in it. There is a sand shoal at the exit of colds pass, and a long shallow shoal running across the back of Christmas. Make some waypoints on Google earth.. it's also already marked on Reef Recon... might not be a bad investment in that boat.. all the reefs in Bastrop, Chocolate, Christmas, West... and more are all marked and would show up on your GPS.