title pretty much says it all. my boat (allegedly, by prev owner) does 63 at 6000 with 23 inch props. computes to 27% slip. Mirages. no. not the Hatteras.

I'd say 10-12% is pretty dialed in.

You sure you have the drive ratio correct while figuring?

What motor? Thought it was a stock 502? 6k is way to much. Now if that's at 5k then it's 13%and all ok.

Just to get it out of the way. Prop slp depends on the application and hull. Some hulls like slip, some don't. So to say all boats need a low slip is incorrect. Some of the newer Fountains for instance, run well and fast with a slip of 15-16%+. If it's your Nova, yes everything from 8-12% is good with a clean bottom and drive, depending on setup and weight. What motor, drive and ratio are you running and have you verified your tach, GPS and gear ratio?
What can affect slip? Bottom condition for one. Dirty, rough, painted ect bottoms will cause an additional slip, that's life. Damaged bottoms, hooks ect. as well. Or course the condition of the prop itself and the x-dim. If your 27% is indeed correct, you are way too high. One cause can be the non + Mirage's lack of cup. How high is your x-dim?

ok, correction time. prev owner told me 63 gps. his friends said he ran it around at 6 grand. asked him today. 5200 at 63 mph. comes out to .165 or so. better, but still a few points out of good. engines are 2 355's. Dart sportsman heads 1.94's. alum edelbrock intakes. performers non-rpm. GLM alum exhausts. LT1 cams. used to be called 327-375hp. last street cam you couild put in a boat. everything from 70's on up is all emissions. he figures 350 hp per side. x-dim. motors are in stock location. i hope wellcraft had a clue when they designed it. from what i hear, though the step in the hull was counterproductive...and who the heck is BONNIER?

Bonnier is the corp. that screwed all it's subscribers over and are responsible for Powerboat mags end. So therefore that statement.

I don't recall the stock location, it sometimes varied if a dealer ordered a boat with a higher x ect. My guess is it's around 14½". That will put the prop shafts about 7½" below the bottom. Does that sound about right? In the light that your slip is 16,5%, a Mirage+ 23" or a 4 blade, either Revolution4 23" or Bravo1 24" would be worth a try. Depending on where your powerband is, lower pitch props might be needed, since the 4 blades will take about 200+ rpms off your current rpms. The M+ will lower the rpms about 100 or so rpms over the old style Mirage. How does the boat handle with the current props? Blow out in turns, ventilating out of the hole ect? If it handles ok now, you could look into having Bblades lab your current Mirages if they are in good shape. Give him a shout.