http://www.propgods.com/content/propellers.aspx

I posted this in another thread, but it gives you a general idea of what MERCURY's props do. The MIRAGE is designed for large heavy boats with big HP, the V-20 isn't exactly big and heavy. The REV 4 is designed for lighter boats and top end. The VENSURA is similial, but is basically a 4 bladed MIRAGE.

if your trying to get the bow to lift, what about a tempest? I've never had much luck with them on boats I've tried them on, but I figure they must work on something otherwise they wouldn't still make them. they have more blade surface than a laser, and seem to work better on heavier boats liek the V(vs a bass boat). As far as four blades, my experiance has been they will lift the stern, pushing the bow down, unless its a high rake fourblade and they generally work better on light boats. If you can't find a 23 Mirage to try, carry your 21 to a prop shop, tell him you need 200 rpms less and soem bow lift, a good shop should be able to dial it in on teh prop you have.

Thanks Ridge. I would have to say it was nothing more than an educated guess based on the speed of my v with its 225. You can never have too much power. Those 3L Mercs do sound mean don't they. Lots of luck with your new setup.

Prop Gods recommended a Tempest in a 23p. My prop slip was 14% not 11% as reported. They suggested the Rev-4 was not faster than the Mirage in their experience. Tempest has the same blade design as the Rev-4 just 3-blades with lots of bite. The Tempest turns a few more rpm than the Mirage in the same pitch. Prop is on the way for testing..
Keep you posted.

You may need to raise the engine even more with the TEMPEST from what I've heard about it. It likes to run with a little air in it to help it spin up.

Thanks Ferm, I appreciate the input. With the Mirage, I had to lower the motor one hole from the top as the prop was starting to loose bite in the turns. Water pressure was down a bit too. Right now it is one hole from being as high as it will go and still have adequate water pressure. I will see what it will do. I may just need a little tweeking on the Thunderbolt, as suggested by Ken.

Prop arrived today from Ken @ Prop Gods. Excellent service... I have had to wait longer for a gallon of 2-stroke oil from my local shops. Test time.

The answer to the question is ...... wait for it ... Yes, the way to make it run much faster than 50 is to buy and use more hp. Saturday I was anxious to run my 20v cc with the 250 EFI Merc on a 30" setback bracket. The weather was perfect, wind 4-5mph out of the north creating a very light chop and a cool 69 degrees at 8:00 am. Took a snapshot of the boat in the water and proceeded with testing. Light setup for the test, one person, cooler full of drinks and ice, 1/4 tank of fuel, no water in the holding tank.
The first 20 minutes was for warm-up. The 23P Tempest gets the boat out of the hole very well. It cruises at 40mph at 4000 rpm. WOT with no trim gives 5300rpm at 54 mph. Add trim and she starts to fly the bow. Best speed into the wind was 60.4mph. With the wind I saw 62.0mph. The speed was measured by GPS. The motor would accellerate hard to 58 and then take another 15 seconds or so to climb to the max velocity. The boat chine walks a little above 58 but can be driven past it. I attempted a few pictures of the GPS at speed. I got three pictures at 61.6mph. I saw 62mph a couple times but never got the picture. The refresh rate on the Lowrance was trying to keep up with the speed IMO.
The speed kept increasing until it finally hit the limiter again at 6000 rpm.
It may still have a mph or two in it but I am really done now. I bought the prop as I found bottom in the lake twice while trying to find my dry box that blew out of the boat whan I wasn't looking. Special thanks to Shaun Torrente (best driver I have ever seen) for selling me a hoss of a 250 Merc, Fred Van Wagoner for the fairing and paint job on the boat and my loving wife who has no idea how much all this cost. A few others for their input and support, Ferm, Spare and last but not least wellcraftv20.com. It was fun. On to new thinks.:beer:
Pics Attachment 1450

Attachment 1451

OK, I guessed 59, any one closer? And I guessed the tempest, although I didn't have a lot of faith in it. Good to hear you hit the numbers. On a bet, I would have figured the Mirage would have given the best numbers, good to know what props work

I haven't seen the rating on a 70 model, my 1972 was rated for twin 115's on the transom info plate.