I have 2 propellers I have tested. I would like to have everyone's thoughts on which one I should use and why. I plan on having HoustonProp/Throttle Up or York Propellers lab and or rework the props to maximize them...So I need to take into account that one might outperform the outher if reworked (cup,pitch,thickness or diameter etc.)
The first prop is a 14 3/4 X17 Michigan Ballistic. The Second is a 14 3/4X21" Quicksilver Mirage (not plus). This prop is a Solid Hub though. I got the prop given to me and it is in great shape. The majority of my boating is down in areas with no stumps or logs to worry about. My motor is a 358 SBC pushing about 360hp. Boat is a 1986 22ft. Formula(a real anvil.)It weighs about 4100lbs loaded. Maximum power is at about 5200rpm's
Here are my results.

Ballistic/ Mirage

Rpm's-mph---/ Rpm's -mph-difference

3000-28mph---/ 3000-33.5mph=+5.5mph
3500-34.5mph---/ 3500-40.5mph=+6.0mph
4000-41mph---/ 4000-45.5=+4.0mph
4500-45.5mph---/ 4500-53.5=+8mph
4600-46.5mph---/ 4600-54.0=+7.5mph
5100-55.0mph(Max RPM)-/ Mirage MAX'S OUT @4600

Tests were done on same day with Smooth as glass water with 77 degrees and mild humidity. 1/4 tank of gas and 2 people (normal load). All done per G.P.S.

Some observations..The Ballistic had nice acceleration and got the boat on plane accectable. The Mirage was a DOG out of the hole and was very sensitive to trim under 3500rpm's. After that It took a LONG time to wind out and wanted all the trim I could give.I got my most speed with the drive trimmed out as far as it would go which was just under 1/2 way on my guage. Im sure it probally wanted a little more trim. (Is there a limit on the drive and the amount of trim?)The Ballistic wanted about 3/8th of the way out on the trim. Sooooo there is my results what should be done and what can be done???? Im running a Alpha drive with a VERY conservitive X-dim so running a 4 blade is probally out. I want to work with these two props if possible.

Thoughts,comments anyone?
BH a.k.a. Randy......

I would use the trailer button and run the mirage again with as much trim as it will take. Watch the gps and when it starts to loose speed you have over trimmed. The prop will blow out long before you hurt ujoints. You may in fact get more rpm out of the mirage with more trim.

Also, something is funny with your numbers. With the ballistic your numbers represent -4.14% slip, which is impossible. The mirage computes to 6.53% slip, more possible but still unrealistic. 12% would be an excellent slip figure for your boat. I would check the tach accuracy because something ain't right unless you are doing this in a river with 10 mile per hour current

BT

I agree with BT, something is fishy about those #'s. Is the ballistic really a 17 or is that a typo and were you comparing a 19 to the 21 Mirage? What gear ratio is your drive?

I'm running a similar boat/motor combo (89 Mach 1, 23'8", 406 small block dyno'd @360 hp) I've been running a Michigan Wheel Rapture 21 at about 5200rpm/55mph. Last weekend I tried a 23 Mirage, and got 5000 rpm, but only 54 mph. I don't know why but my boat didn't seem to like teh mirage.

It seems to me that you should be able to run a 21 up to 5000+rpm.

Regards
Mike

I can't get your figures??? I have been told by York Propellers that the way the Ballistic is made it really is more like a 18". Tach is correct....I actually have 2 tachs hooked up. One in the engine compartment and my dash tach.The ballistic is a 17" It is quite the odd prop. Gear ratio is a 1.5.....I went to the BAM site and put in my figures and got a Theoretical top speed of 61 with the Mirage and 59 with the Ballistic. Slip was 13% with the Mirage and 7% with the Ballistic. Rpm's were 4600 for the Mirage and 5200 for the Ballistic.

BH

http:\\www.go-fast.com/Prop_Slip_Calculator.htm

Good point Oly. I used a drive ratio of 1.5, but if it is 1.36 it would be much closer to 12% slip. In fact the 21 pitch would be getting to the 59mph range. Let me know what the ratio is BH and I will plug the numbers in again.

BT

It's a 1.5...I even had it checked when the drive was apart a year or so ago....

BH
a.k.a. Randy

Here is what my home grown calculator says:

---------------------------
MPH
Input:
rpm 4600
pitch 21
constant 1056
gear ratio 1.5
slip % 12



Output:
mph 53.67
----------------------------
BAMs theoretical speed (0% slip) 61mph * .87 (13% slip) = 53.07 mph.
----------------------------
We are saying the same thing BH.

BT

Wheeewww....Glad we got that straightend out I still need some advice though

Thanks
BH

We gotta get the facts straight first BH. Now if your mirage had been previously repitched to a 22 (fairly common), you would be close to your numbers with 12% slip:
---------------------------------
MPH
Input:
rpm 4600
pitch 22
constant 1056
gear ratio 1.5
slip % 12



Output:
mph 56.22
-----------------------------------
What do you think? (P.S. if you want I can email you my prop calculator. It is quite accurate and easy to use on excel)

BT

Is 12% a reasonable assumption for slip. That seems pretty low for a heavy older v. I guess it's possible with all the trim that the Mirage liked.