Goofy1103

Which setup would perform better or would it be almost equal ?

Bravo 1 Prop 28 Pitch Lab Finished and Bravo 1 XR 1:35
or
Bravo 1 Prop 30 Pitch Lab Finished and Bravo 1 XR 1:50

Triple HP 525 on a 13000 pound V Bottom with Boxes and High X Dimension

carney

I would call Chris Martin . HE KNOWS DRIVES. he rebuilds them and ships them all over. Pm my if you what his number.

tomcat

I assume that you have results with one of these combinations. If you can tell me current top speed and RPM with your current combination I can shed some light on this with a graph. Are these 525SC or 525EFI engines?

cobra marty

I say the 28" prop because I think that it is the most efficient pitch but you will probably get a 50/50 split. To each his own.

bbladesprops

My suggestion would be to go with the 30's and the 1.5

Your throttle response will be sharper. Your speed will be the same taking into consideration all box stock props are different although they are not supposed to be.

Brett Anderson / BBLADES Professional Propellers, LLC.

tcelano

Goofy1103,

My simulation software shows that 30"s with 1.5 gears are not quite enough for your setup. I have made some assumptions in the inputs about your boat and motors, but below is close to what your boat should look like with 31"s on 1.5 gears. (Assumed power curve for HP525SC...) Note that the power curve assumes you aren't dragging the trim tabs.

You can run the code yourself at www.speedboatperformance.com.

Performance Prediction Input Summary

Manufacturer: X

Model: X

Length: 42 ft

Beam: 8 ft 6 in

Weight: 13000 lb

Deadrise Angle: 24 deg

Hull Depth: 6 ft

Number of Running Strakes: 4

Number of Transverse Ventilated Steps: 1

Hull has a keelpad

Boat has an open cockpit

Engine information:

Boat has 3 x 502 c.i. Normal engines installed

Engine Redline: 5400 RPM

Peak BHP is 525 BHP occuring at 5300 RPM

Peak Torque is 550 lb-ft occuring at 4200 RPM

Drive information:

Boat has 3 x Bravo One, X, XZ, XR Drives Installed, with 1.5:1 gears

Propeller information:

Propeller: 4 bladed Bravo 1

Prop Diameter: 15.25 in

Prop Pitch: 31 in

Prop is set 30 inches behind, and 5 inches below the running surface

Environmental Conditions:

Boat is to be simulated operating in Salt Water, at 0 ft above msl, with an ambient air temperature of 80 degrees F

Program Completed

Computational Results
Your boat's computed performance is as follows:

SPEED(mph), ENGINE RPM, REQ'D BHP, AVAILABLE BHP, PROP ADVANCE, WETTED LENGTH(ft)

25.00 1988 212 522 0.632 22.72
26.00 2042 223 541 0.640 22.88
27.00 2097 234 560 0.647 23.09
28.00 2154 247 579 0.654 23.37
29.00 2206 258 598 0.661 23.19
30.00 2254 266 615 0.670 22.54
31.00 2305 276 633 0.677 22.16
32.00 2353 285 651 0.684 21.57
33.00 2405 296 669 0.691 21.24
34.00 2453 306 687 0.698 20.69
35.00 2505 318 706 0.704 20.40
36.00 2553 328 724 0.710 19.90
37.00 2602 339 743 0.716 19.42
38.00 2655 352 762 0.721 19.19
39.00 2704 363 781 0.726 18.75
40.00 2753 375 800 0.732 18.32
41.00 2803 387 818 0.737 17.92
42.00 2855 401 838 0.741 17.74
43.00 2905 414 857 0.746 17.36
44.00 2955 428 876 0.750 17.00
45.00 3005 441 895 0.754 16.65
46.00 3058 458 916 0.758 16.51
47.00 3108 472 935 0.762 16.19
48.00 3159 486 954 0.766 15.87
49.00 3209 501 973 0.769 15.57
50.00 3259 517 992 0.773 15.28
51.00 3310 533 1011 0.776 14.99
52.00 3361 549 1030 0.780 14.72
53.00 3415 568 1050 0.782 14.64
54.00 3466 585 1069 0.785 14.38
55.00 3516 602 1088 0.788 14.13
56.00 3567 620 1106 0.791 13.89
57.00 3618 638 1125 0.794 13.66
58.00 3670 656 1143 0.797 13.43
59.00 3721 675 1161 0.799 13.22
60.00 3772 694 1179 0.802 13.00
61.00 3824 713 1196 0.804 12.80
62.00 3878 737 1215 0.806 12.76
63.00 3930 757 1232 0.808 12.57
64.00 3982 778 1249 0.810 12.37
65.00 4033 799 1265 0.813 12.19
66.00 4085 821 1281 0.815 12.01
67.00 4137 843 1297 0.817 11.84
68.00 4189 865 1312 0.819 11.67
69.00 4241 888 1327 0.820 11.50
70.00 4293 911 1342 0.822 11.34
71.00 4345 935 1356 0.824 11.18
72.00 4397 959 1369 0.826 11.03
73.00 4449 984 1382 0.827 10.88
74.00 4501 1009 1395 0.829 10.74
75.00 4553 1035 1407 0.830 10.60
76.00 4606 1061 1418 0.832 10.46
77.00 4658 1087 1429 0.833 10.33
78.00 4711 1114 1439 0.835 10.19
79.00 4763 1142 1449 0.836 10.07
80.00 4819 1175 1458 0.837 10.07
81.00 4872 1203 1466 0.838 9.954
82.00 4924 1232 1473 0.840 9.833
83.00 4977 1262 1479 0.841 9.716
84.00 5030 1292 1485 0.842 9.600
85.00 5082 1323 1490 0.843 9.488
86.00 5135 1354 1494 0.845 9.378
87.00 5188 1386 1496 0.846 9.270
88.00 5241 1418 1498 0.847 9.165
89.00 5294 1451 1499 0.848 9.062
90.00 5347 1485 1499 0.849 8.961
90.38 5368 1498 1498 0.850 8.862


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Goofy1103

Engines will be 525 EFI
I have now 496 HOs with 26 Bravo I lab finished props at Bravo 1 X running 73 MPH at 5150 RPM (rev limiter)
I already own a set of 28 lab finished Bravo 1 Props - so when buying new engines I might keep the 28 props with 1.35 gears

Thanks for the input so far

throttleup

Given your current numbers with the 496 HO and anticipating the increase in power with the 525 I would definitely go with the 1.5 gears. I would estimate your top end speed to be about.83-85. If you had a very efficient set up you should be able to run this speed with the 28 Bravo 1 lab props with 1.5 gears. More likely you will need either a stock 28 Bravo 1 or a lab finished 30 that may need to be down pitched a little or your 28 Bravo 1's could be up pitched a little.

I would start with the 1.5 gears and the lab 28's you have now to get a baseline number and go from there.

Matt

cobra marty

Interesting that speedboatperf predict 90mph and Throttleup 83-85. You actuat results will be very interesting.

throttleup

To gain almost 20 by adding 125 hp per motor would be highly unlikely.
We have a several customers with boats in the 42-47 foot range with triple 525's and they are in the 82-87 mph range.