jcap

The number of blades does not change the theoritical speed only the pitch does ,(theoriticaly, diameter doesnt change it either) it is the slip number that will change ,lower slip with greater number of blades , if hulls could be 100 percent efficient all props of the same pitch would produce the same speed. At 100 percent efficiency a 25 pitch prop will travel 25 inches per revolution regardless of diameter or number of blades, of course we know that dont fly in the real world. More blades mean more thrust produced, improved technology has allowed manufacturers to only recently produced 5 and 6 blades at a more reasonable price

Boat max speed

It took a long time and a lot of work to get my boat to break 90, people said the Y2k was maxed at 80 85. It is a little squirrely at 85 with a bravo 4 blade and damn scary with a three blade , with a 5 blade 90 feels like 70 , I can remove my hands from the wheel in a chop at 90 and its straight and very controlable

The law of diminishing returns will make it harder and harder to gain mph the faster you go, to get a modern deepv hull to go 5 mph faster will require much more hp if you are doing close to the hulls maximum designed speed; if it takes 25 hp to increase wot speed from 60mph to 61 mph in could take 50hp to raise speed from 70 mph to 71 mph and the formula gets worse the higher the speeds , diff hulls vary greatlyt but you get the idea.

Jim

Pat McPherson

Hey Jcap,
Why do boats handle better with 5 blade vs. 4 blade vs. 3 blade props?
My boat is much more stable with the 4 blade vs. 3 blade even at my comparatively slower top speed of 67mph...
I thought with my boat it was mostly do to the stern lift vs. stern down effects.
Please enlighten us oh prop guru Jim...
Thanks,

SUPERBASH

Good info once again from SUPERBOAT GURU'S PAT & JCAP!

-(Jim...my boss just ran into a guy at a construction job going on. He said he races a 30' SUPERBOAT...& had SUPERBOAT stickers all over his truck. Any idea? That is the only info I got.)

FX10

Could it be John Jr. ? Supergutter

FASTERDAMITT

JCAP,
This is getting interesting guys. Since I plan on running 90's these are issues I need to know and was unaware off. I just took a trip to New York and could not drive a Y2K because nothing was available. JCAP, your runnin 90's now. (squirlly with a Bravo1?) My initial opinion (gathered from other board menbers and..) was that the Y2k was stable at these speeds. If all it takes is a 5 blade prop then maybe it's no issue. If I'm going to put my passengers in danger on a spontanious drag race showing off my Superboat's potential then maybe I'm lookin the wrong direction. Honest imput please!

Superbabi

Jcap, You Really Have It Down With Speed-prop-hp Equations. What Do You Think I Will See With Superbabi ? Mods. Blueprinted Bottom- Whipple #2 Upgrade. Say Total Hp At 450-460.and 5blade Hydro.

Pat McPherson

I corresponded via e-mail with Matt at Throttle Up today about how a 5 blade might run on my 24' Super.
I told him that my boat tops out at 67mph at 4600rpm with a 26p Bravo I.
Then I told him that I know of other Superboats that see 73mph at 5000rpm with the same prop.
He told me that with the slip number calculated from the info I gave, a 5 blade prop was not the way to go.
I did not ask about the handling difference between the two; but if brother Jcap does not come back to us on the subject, I might have to...
Come on Jim, why does your boat handle soooo much better with a 5 blade?

SUPERBASH

Pat

I did have a MERCURY HIGH FIVE 5 blade prop on the 21CC on it when JC gave it to me. He tried to use it to smooth out the boats quirk. It was definately a "smoothening" prop & handled best. But wasn't designed for top speed...unlike the hydromotive.

Pat McPherson

I couldn't wait for you Jim...

From Matt at Throttle Up:

Patrick,
Yes, 5 blade props handle better than 4 and 6 better than 5. The reason is you have more blades in the water at any one time. Rough water handling, plane-off, turning, maneuverability and cruise speed are better with a 5 blade. If the drive height is not optimized for the boat and propeller then there could be a loss of top end speed with the 5 blades. But every other aspect of the 5 blade prop would be better.

Hey Dave M.
What do you think? Got an extra $1000 in the budjet?
I know we both need new props....

jcap

That truck with the superboat stickers sounds like John Jr, Supergutters is his business gutters and leaders

Fasterdammit,
I am pretty straight about superboats and have pissed people off for being honest about some complaints about superboat(hey man you gonna mess up resale value) but the truth is dollar for dollar it is the best value out there, my boat was originaly set up as a APBA f-1 boat designed with 500 hp and about 80 mph, when I went to 650 - 700 hp the set up had to be tweaked, the bravo1 prop was no longer the best prop , with the P5x five blade I have let my 12 yo son and my wife drive at WOT between 89.5 and a best of 91.0mph and I have more but I choose to set limiter at 5600rpm and boost to 4psi. I am a safety freak and would never endanger family for my speed fetish! The narrow beam has some downsides but these boats are truly amazing in the rough, that is where i believe they truly shine , if you want to just go fast buy an Allison with an eggbeater(awsome lake boat), but if you want to go fast in snot there is nothing better in the 28 to 30ft single engine catogory, and yes I think I could be in the triple digit club if i raised boost and upped the rev limiter.But I prefer to do 75 in 5 footers than 95 on glass. I get my ass kicked by 28 foot skaters on the great south bay all the time but when we go out the inlet its a different story , I am not saying I am faster than a skater but I can run faster in the real nasty ****.