Merc vs Hyromotive Props
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02-16-2002, 03:16 PM
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It really dpends on your boat. Whether or not you need the bow lift(Bravo prop) or the stern lift(Hydromotive). My Checkmate handles better and is faster on top than the Bravo1 prop. AS Im sure you know, best thing to do is try them all!
Eric
Eric
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02-17-2002, 10:47 AM
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I picked up a couple of miles per hour with the hydromotive over the bravo. The Hydromotive was much more stable on the top end than the bravo. With the Hydromotive it was almost impossible to get on plane whereas the Bravo would just slip-sometimes alot, but never blow out. The Hydromotive also threw a blade after 3 hours of use.
02-18-2002, 12:47 AM
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HI,
I've found the 5 blade hydromotives superior to the Bravos in my current set up. Prior to adding blowers, the Bravos were superior. It does seem to be the case that each boat will react differently to different props. In my case, when the boat was running in the low to mid 80's at WOT (trip. 500 EFI's) the Bravo 4 blades, labbed at 3.15 inch were the best running about 14% slip.
When we Whippled the boat and started running near 100 at WOT, we changed to 36" Bravos. Slip increased to almost 24%. We then changed to 1.35 gears from 1.50 and dropped to 34 inch props. Same WOT and same slip.
Then put on the 5 blade hydromotives 15.50 X 32 and slip dropped to less than 9%. Getting on plane was a snap, no cavitation, stayed on plane at 2200 RPM.
I did not expect the pleasant results, and it just reaffirmed that testing on your particular set up is the only way to know for certain. If any of you would like to test the larger Bravos, 34 or 35 inch labbed, I have a couple available and would be happy to lend them to you for testing purposes. If they work for you, you can buy them, and if they don't, just send them back.
Take care,
Steve
I've found the 5 blade hydromotives superior to the Bravos in my current set up. Prior to adding blowers, the Bravos were superior. It does seem to be the case that each boat will react differently to different props. In my case, when the boat was running in the low to mid 80's at WOT (trip. 500 EFI's) the Bravo 4 blades, labbed at 3.15 inch were the best running about 14% slip.
When we Whippled the boat and started running near 100 at WOT, we changed to 36" Bravos. Slip increased to almost 24%. We then changed to 1.35 gears from 1.50 and dropped to 34 inch props. Same WOT and same slip.
Then put on the 5 blade hydromotives 15.50 X 32 and slip dropped to less than 9%. Getting on plane was a snap, no cavitation, stayed on plane at 2200 RPM.
I did not expect the pleasant results, and it just reaffirmed that testing on your particular set up is the only way to know for certain. If any of you would like to test the larger Bravos, 34 or 35 inch labbed, I have a couple available and would be happy to lend them to you for testing purposes. If they work for you, you can buy them, and if they don't, just send them back.
Take care,
Steve
02-18-2002, 08:33 AM
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Steve,
What kind of boat did you put the 5 blade props on?
Did your RPM stay close to the same with the 5 blade 32" and the 4 blade 34"?
Do you know the dimension from your prop shaft to the hull and are you using any standf boxes?
I running an 28' Eliminator cat and need to change props because the 32" 4 blade bravos and 1.25 gear are not enough with hydraulic lifters. I also heard the new 5 blades picks up a lot in the mid range but about the same as a bravos on the top in, is that what you saw?
Seeing how I run in the mid range 95% of the time, these might work out for me, if not I will be looking at a pair 34" bravos.
Randy
What kind of boat did you put the 5 blade props on?
Did your RPM stay close to the same with the 5 blade 32" and the 4 blade 34"?
Do you know the dimension from your prop shaft to the hull and are you using any standf boxes?
I running an 28' Eliminator cat and need to change props because the 32" 4 blade bravos and 1.25 gear are not enough with hydraulic lifters. I also heard the new 5 blades picks up a lot in the mid range but about the same as a bravos on the top in, is that what you saw?
Seeing how I run in the mid range 95% of the time, these might work out for me, if not I will be looking at a pair 34" bravos.
Randy
02-19-2002, 01:13 AM
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Hi Randy,
These are on my 43' Black Thunder, app. 13,500 pounds, power is triple Whippled 500 Efi's app. 740 HP each.
The RPMS dropped almost 250 going to a 32 Hydromotive 5 blade from 34 inch Bravos. The drop is mainly from the increase in efficiency, almost 1/3 the slip. XR drives at 1.35 ratio.
I'm not positive on my X dimension, the hull is stepped, with a notch transom. Instead of conventional stand off boxes, Black Thunder incorporates them into their mold. So to answer your question, yes there are standoff boxes and actual drive is probably a good 24 inches set back from the bottom of the primary running surface and the Centerline of the prop shafts are about 2 inches above the bottom of the primary running surface.
There is no cavitation at anytime getting on plane with the 5 blades. There was some on the outside drives with the Bravo 4 blades.
If you're thinking of going to a 34 inch Bravo, you're welcome to borrow my Bravos (34 inch, labbed) and see what they do for you.
Good luck!
Steve
These are on my 43' Black Thunder, app. 13,500 pounds, power is triple Whippled 500 Efi's app. 740 HP each.
The RPMS dropped almost 250 going to a 32 Hydromotive 5 blade from 34 inch Bravos. The drop is mainly from the increase in efficiency, almost 1/3 the slip. XR drives at 1.35 ratio.
I'm not positive on my X dimension, the hull is stepped, with a notch transom. Instead of conventional stand off boxes, Black Thunder incorporates them into their mold. So to answer your question, yes there are standoff boxes and actual drive is probably a good 24 inches set back from the bottom of the primary running surface and the Centerline of the prop shafts are about 2 inches above the bottom of the primary running surface.
There is no cavitation at anytime getting on plane with the 5 blades. There was some on the outside drives with the Bravo 4 blades.
If you're thinking of going to a 34 inch Bravo, you're welcome to borrow my Bravos (34 inch, labbed) and see what they do for you.
Good luck!
Steve
02-19-2002, 01:30 AM
#9
Hey SteveDavid, What lowers are you running? Stock bravo or IMCO with nosecones. Some say IMCO lowers run 3-5 mph faster due to better hydrodynamics. Hydromotive should put you on the payrole for all the good testing and positive comments about their 5 blades.
02-19-2002, 01:48 AM
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Hi Marty,
I'm running the XR lower unit. As to hydrodynamics on drives, Dean Claussen at the Bravo shop has invested a considerable sum in testing just that issue. Give him a call after he returns from the Miami Boat show. If he's not in, speak with Yvonne and she'll get him to call you back.
It's difficult saying the Hydromotives are superior over the Bravos, after all the years Dennis Cavanaugh and Bob Hetzel have helped me with my Bravo props, and before that the props on my hydroplanes. Dennis really worked with me on trying to get these Bravos dialed in on the BT after the Whipples were added. We must have shipped them back and forth 4 or 5 times and he was tenacious in his desire to help. I'm sure if he was given the budget by the higher ups at Merc Hi-Performance he'd come up with a heck of a 5 blade as well.
Marty, that fellow Bjorn (that bought your EFI stuff) is having a tough time finding a 500 EFI short or long block. If you've got anything, he could use your help. Really nice guy and just can't find anything in Norway. He called me a day late for the long blocks I just sold.
Take care Marty,
Steve
I'm running the XR lower unit. As to hydrodynamics on drives, Dean Claussen at the Bravo shop has invested a considerable sum in testing just that issue. Give him a call after he returns from the Miami Boat show. If he's not in, speak with Yvonne and she'll get him to call you back.
It's difficult saying the Hydromotives are superior over the Bravos, after all the years Dennis Cavanaugh and Bob Hetzel have helped me with my Bravo props, and before that the props on my hydroplanes. Dennis really worked with me on trying to get these Bravos dialed in on the BT after the Whipples were added. We must have shipped them back and forth 4 or 5 times and he was tenacious in his desire to help. I'm sure if he was given the budget by the higher ups at Merc Hi-Performance he'd come up with a heck of a 5 blade as well.
Marty, that fellow Bjorn (that bought your EFI stuff) is having a tough time finding a 500 EFI short or long block. If you've got anything, he could use your help. Really nice guy and just can't find anything in Norway. He called me a day late for the long blocks I just sold.
Take care Marty,
Steve
