24 daytona prop tuning
 

Went out today to test a new 15 1/4 x 24 Bravo 1 prop on my 24 Eliminator Daytona. I believe I am making about 450 HP on a built up 454 Mag MPI converted to Carb with various mods.

*MPH are from GPS
*Slip was calc'd from a web site
*Here are some of my numbers:

3500 rpm - 45.0 mph - 15.1% slip
3730 rpm - 48.5 mph - 14.6% slip
4000 rpm - 53.0 mph - 12.5% slip
4250 rpm - 56.0 mph - 13.0 % slip
4500 rpm - 58.5 mph - 14.2 % slip
5200 WOT - 68.0 mph - 13.6% slip

I ran these numbers with a 15mph head wind and 1' cop, boat seems to need alot of bow lift at these low speeds so drives were trimmed well.


The boat could use some more power to get it up to speed and lighten it up but that takes $. For now I just want to tune the prop to get the best performance between 3500 rpm and 4000 rpm.

It doesn't look like the bravo comes with much cup. Would a little added cup help reduce the slip and build mid rangespeed I could cup the prop and take the WOT down to 5000-rpm.

What do the experts say. Am I looking in the wrong spot?

Re: 24 daytona prop tuning
 

If the prop you tested with is a new prop it should have all the cup a Bravo 1 should ever need. I wouldn't recommend adding more cup to a stock Bravo 1 on your boat. It will just drag down the top end with possibly little gain at mid range.

You also don't want to over prop (too much pitch) a 24 daytona, especially with big power. The work you have done to the motor will determine what the best rpm is to run the motor. If you are looking for a good well priced all around prop I think you have found it.

If you want to invest money in a prop there are many options for you that can certainly add performance and enjoyment to your boating. The numbers for your particular set up seem to be good.

Matt

Re: 24 daytona prop tuning
 

Thanks for your input. I agree that this seems to be a very good prop setup for the boat as it sits. The Bravo 1 did perform very well overall.

I'm new to the boat and it seems to run best at speed with full trim. I am not used to having to run a boat at full trim and am wondering how to get some additional lift at a lower trim angle so efficiency will increase.

Anyone have any thoughts on the new HydroMotive 5-blades that are supposed to provide more bow lift.

Again, thanks for anyones opinions.

Re: 24 daytona prop tuning
 

Have you Dynoed the motor?

What we are looking for is the peak torque RPM and the peak HP RPM. The smallest pitch available in the Hydro P5-X is a 25P. It is a great prop but might be a bit much for you to pull.

Julie

Re: 24 daytona prop tuning
 

Throttle Up
Julie

When proping for top speed, do you prop for peak HP????????
22', 3600 Lb, deep V

Modified HP 500 (9.4 compression and cam retarded 3 degrees)
Desktop dyno
Peak HP around 525 @ 5250RPMs
Peak torque around 627 @ 3500 RPMs

My engine (Desktop Dyno) Stock HP500 Carb
RPM HP Torque HP Torque
3500 418 627 412 618
4000 476 625 464 608
4500 519 605 499 582
5000 534 560 505 530
5500 526 502 485 463

THANKS!!!!!!!!! :D

Re: 24 daytona prop tuning
 

I just bought the boat and do not know if it has been on a dyno. I do not have the data if it has. I did get the build list if that would help with estimating HP and Torque.

Mark V 4 bolt main, std bore
Steel Crank
7/16 dimple rods
J/E forged pistons. 9.8-1
ISKY roller cam. .553 intake lift, .578 exhaust, degreed at 108, 114 lobe ctrs
Hyd. roller lifters
crane roller rockers
square port GM heads
Hardin Dart copy manifolr
Merc 500-hp marine holley carb
mallory magnetic dist.
holley marine elec. fuel pump.

any estimates of HP and torque curves from the group would help with specing a prop. Without this information are there any thoughts. I'm looking for max cruise without going into the secondaries (3750rpm)while still being able to hit solid high speed numbers.

Thanks for your input and thoughts

Re: 24 daytona prop tuning
 

RickR, Yes we prop for peak HP when the goal is maximum top end. In your case a stock HP 500 carbbed needs to run at 5200 RPM. I would think with your modifications you may have bumped it up. What type of modifications are we talking about?

Julie

Re: 24 daytona prop tuning
 

Throttle UP
Julie
HP 500 (502ci) clone with compression raised from OE 8.8 to 9.4, cam intake lobe centerline retarded from OE 105 degrees to 108 degrees, Gil Mag Choice and MSD ignition with 6000 RPM revlimiter.

Currently running Turbo 1 14.25X24" 5450 RPMs

Thanks!!!!!!!!! :D