Testing @ ***boat , An Idea

[Bryan Rose]

Hot boat does a lot of testing of various things from Mufflers to watching an Extreme trailer being built...Pretty good stuff . But I think we all know that a Prop is the single most overlooked thing on perfromance boats. People mostly go with what the manufacturer supplies, IE Brunswick Corp. owns just about everything in the marine world Mercruiser , hence the Bravo I prop and Maximus etc.... these may be the best props out there but it would be nice to see a couple of good tests on some prop types and what they do to each type of hull be it cat deep V step hull mod V etc.....sure would be nice to see it or maybe it is just not possible. they did it with cyclones jet so I would think they could do it with a couple of boats .... All of the prop makers say test every prop you can but it is difficult to get them to step up, oh that prop is out or we don't have it in that pitch.
I for one know just enough about props to be dangerous, I would like to know about how rake and cupping effect each type of hull ,perhaps how a prop acheives bow lift or stern lift on a perspective hull. Maybe how the diffuser ring help or hurts the props performance. I guess I am just Prop Ignorant......
Flame away I am wearing a suit made of asbestos
What do you think?
Bryan

[LHC30Victory]

Good Idea - especially if I could get HB to front the $$$$ for a pair of Hydromotive P5X's for my boat. You know, just so they could get the right ones

[Bryan Rose]

Test conditions
1997 Donzi 27 ZX twin step
Merc 500 EFI Blue motor
Bravo I drive
Temp 98 degrees
Humidity 85 %
wind calm
water smooth , no chop at all but not glass
Boat 1/3 tank of 100 gallon load
me 220 lbs
MIxed at this point. I went to my little local lake today and gave it a try. Blistering top end compared to my Bravo I .
Bravo I 24 pitch = 5400 @ 67.1
Hdromotive 26 pitch = 5050 @ 72.2
Cruise was much better
Bravo = 4000 @ 48-50 consistant
Hydro = 4000 @ 58-59 consistant
out of the hole good with the Bravo I
with the Hydro better but not great.
Bravo blow out at will.3-4000
Hydromotive worse with the blow out at the same revs.
The hydomotive seems to be a great prop out of the box....But it needs a longer more subtle diffuser ring to get hooked up better under 4000 revs... a real pain in the ass....Also it tends to porpoise more than the Bravo I , actually a lot worse, in all fairness it seems that my test conditions were not that great, no boats on the water , small local lake 6 miles end to end, and smooth water, not glass but smooth, no chop at all just a slight breeze. I am guessing that with a little chop maybe a foot or so and I will pick up a little on the top end and the porpose will subside, all this acording to Tom from Hydromotive.
Am I happy? maybe , I will have to test it in better conditions over the weekend if I get a chance, just wish it would hook up better between 3-4000 for testing , it makes it kind of a pain because you have to get to the other side of 4-4500 and then come back on the throttle.... but I want to test in chop to verify the porpoise problem gets better.
On a side note the Bravo likes to chine wald at WOT and really sucks... I have been able to setlle bot the chine walk and the porpoise with the K- planes but until I get indicaters for them I don't like to mess with them too much, don't like not knowing where they are.....
I am thinking if I can get it not to porpoise in the chop it may be the prop for me, once the prop is swapped out for one with a longer diffuser ring, then Lab it pick up another 200 revs puts me at about 74-75 MPH in the chop......Not to bad for a hull that is 28' and weighs over 7000 lbs and is running a single bone stock Merc 500 EFI....
Thanks for your attention.
Bryan

[plaster dave]

9-10 mph is a great pick up in your cruising range.

[Bryan Rose]

9-10 mph is a great pick up in your cruising range. Thats what I am saying does not make sense but is is a huge difference. The Bravo I is stamped a 24 but I have been told they really are one pitch power in reality.