Ok, so I just took my (new to me) boat out this weekend. Its a 1988 Wellcraft Nova Spyder 26 with a 454 mag (365 hp) and a bravo 1 (1.5 ratio) drive.

Right now Im using a 23p laser 2 prop and its hitting 4500 rpm with 3 adults and 1/2 tank of gas which is just under where I should be (WOT range is 4600-5000) and according to my speedo (not gps) Im hitting 50 mph. I get on plane easily and never really use my tabs. My boat should weigh about 4400 lbs dry.

According to the prop slip calculator my prop slip is 23% which is high IMO. I know if I go with a 23p Mirage plus Ill loose rpm's because its a larger diameter prop compared to the laser 2. So, it seems to me I need a 21p prop. Looking for suggestions--21p Mirage plus? 21p Mirage? 21p Laser 2? Should I just lab my current 23p Laser 2 prop to get the additional 200 rpm's I need? What would get my rpm's around 5000 and get me the best speed? If I can get my slip down to 15% my speed should be around 55-57 mph which I would be happy with.

Suggestions?

You gotta start with a GPS speedo. For kicks throw on another tach, like a timing light with one incorporated, to verify RPM too.
I have a handheld GPS(probably needs batteries) and timing light you can borrow. Call me at the shop.
Rob 425-313-8956

I would probably try a 21 Mirage Plus if your numbers are close to being correct.

Without verified accuracy of the tach and a true GPS speed, you are just guessing though.

The diameter of the Laser II is too small to carry the weight of your 26 Wellcraft and handle the torque of your big block. You need more disc area. As mentioned above, I think the 21 Mirage Plus will be the prop for your application.

Kurt