Prop testing : looking for opinions
07-29-2002, 07:43 AM
#11
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Chuck, that rpm difference really surprises me.
that cam must be pretty peeky, sounds like the 26" just let's it get into the power band and then really screem. do you have the dyno curve to post. us engineers like to bench engineer with data.... NEED MORE DATA........
you could slightly cup the one you have too. effectively adding 1/2 to 1" of pitch. who did the labbing?
that cam must be pretty peeky, sounds like the 26" just let's it get into the power band and then really screem. do you have the dyno curve to post. us engineers like to bench engineer with data.... NEED MORE DATA........
you could slightly cup the one you have too. effectively adding 1/2 to 1" of pitch. who did the labbing?
07-29-2002, 02:16 PM
#13
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Rob,
Yes I was surprised to, but with the 26 being labbed already the rpm spread does kind of make sense.
Here's the dyno data from my 502 which had the same components as the 540 with less compression:
4600rpm 561 ft/lb 493 hp
4800rpm 567 ft/lb 506 hp
5000rpm 569 ft/lb 541 hp
5200rpm 571 ft/lb 574 hp PEAK TORQUE
5400rpm 566 ft/lb 590 hp
5600rpm 560 ft/lb 614 hp
5800rpm 556 ft/lb 620 hp
6000rpm 552 ft/lb 625 hp
Jr.
Call Lenny at Millennyum Marine 468-7361
Yes I was surprised to, but with the 26 being labbed already the rpm spread does kind of make sense.
Here's the dyno data from my 502 which had the same components as the 540 with less compression:
4600rpm 561 ft/lb 493 hp
4800rpm 567 ft/lb 506 hp
5000rpm 569 ft/lb 541 hp
5200rpm 571 ft/lb 574 hp PEAK TORQUE
5400rpm 566 ft/lb 590 hp
5600rpm 560 ft/lb 614 hp
5800rpm 556 ft/lb 620 hp
6000rpm 552 ft/lb 625 hp
Jr.
Call Lenny at Millennyum Marine 468-7361
07-29-2002, 04:14 PM
#14
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TOMCAT has a program that takes this power curve and overlays boat speed knowing your hull efficiency ( 80.4 @ 5600) that will estimate if another pitch will improve the top speed. the program assumes equal prop efficiencies.
now that I see this. you are not falling off your power curve, so you may be at your best point now. One could argue that dropping pitch may increase your speed because your power curve is still climing, but that, I think, is the opposite of what you were considering for reliability.
now that I see this. you are not falling off your power curve, so you may be at your best point now. One could argue that dropping pitch may increase your speed because your power curve is still climing, but that, I think, is the opposite of what you were considering for reliability.
07-29-2002, 05:46 PM
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Rob
Seems like i did a pretty decent job of dailing this boat in !
I will probably just leave it alone and use it for the rest of the summer. I think the motor is coming out this winter to freshen it up (100hrs
) and I will probably dyno it . Then I will really know if I'm close on my tuning.
Seems like i did a pretty decent job of dailing this boat in !
I will probably just leave it alone and use it for the rest of the summer. I think the motor is coming out this winter to freshen it up (100hrs
) and I will probably dyno it . Then I will really know if I'm close on my tuning.
07-29-2002, 09:25 PM
#18
Lab the 28 and you should pick up the 300 rpm that you need. I just went from labbed 26 bravos to unlabbed 28's and the rpm's went from 5600 to 5100. I intend to get the 28's labbed soon and then the 26's will be available.
07-29-2002, 09:56 PM
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SteveJohns,
I would rather take it apart then have it come apart
I run this motor HARD , even though it gets valvesprings and lifters (big solid roller) every season I would still like to go thru the short block.
Anyone have a labbed 28 Bravo one RH that I can try ?
I would rather take it apart then have it come apart
I run this motor HARD , even though it gets valvesprings and lifters (big solid roller) every season I would still like to go thru the short block.
Anyone have a labbed 28 Bravo one RH that I can try ?
Last edited by 26scarab; 07-29-2002 at 09:59 PM.
