Re: 420 over reving?
 

I know there are 2 different Mirage props. The Mirage Plus holds the water a little better than a Mirage. The Bravo 1 4 blade is far better than either of those though. I know you can run Bravo's on a TRS but it may require an adapter. I ran Hydromotive on TRS and you had to use a special thrust washer behind the prop.

Re: 420 over reving?
 

What does going from a 3blade 23P to a 4 blade 23P do for a boat?

Re: 420 over reving?
 

Normally it'll increase cruise speed 5 or 6 mph because of the better bite and give you about the same top end. However, because you're so far over your power peak right now, it should increase your top speed a little too. I'm surprised the prop experts haven' chimed in. You should call Throttle Up Propellors for expert advice.