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-   -   When it comes to props I'm lost..... (https://www.offshoreonly.com/forums/prop-talk/315674-when-comes-props-im-lost.html)

sleev-les 07-22-2014 07:00 AM

When it comes to props I'm lost.....
 
My cig is running Bravo 1's with 1.50 ratio. I have 4 blade stainless 26p props on it. I also have a spare set of props that the previous owner said are more top end, but when I look at them I can only see a marking that say's 23p. They are 4 blade and look more like the cleavers I see on some of the boats. Owner says they were labbed too but trying to figure out how I determine that. I'll try to post a picture later tonight because I think I'm missing something. I though a higher pitch would be more top end. ???

HyFive578 07-22-2014 08:06 AM

Lower pitch will allow you to spin the engines to a higher RPM, thus more speed.

sleev-les 07-22-2014 08:14 AM

So, if my 502's are rated to top out at 5000rpm

A 26p at 5000rpm allows 70mph
A 23p at 5000rpms allows 73mph (not actuals, just for conversations sake)
?

I guess the confusing part to me is that my engine spec sheets say 5000rpm should be the top, and I can get that out of my 26p prop. If the 23p can spin the motor higher, that could potentially be bad? And they'd be the wrong prop anyway?

4bus 07-22-2014 08:36 AM


Originally Posted by sleev-les (Post 4157612)
So, if my 502's are rated to top out at 5000rpm

A 26p at 5000rpm allows 70mph
A 23p at 5000rpms allows 73mph (not actuals, just for conversations sake)
?

I guess the confusing part to me is that my engine spec sheets say 5000rpm should be the top, and I can get that out of my 26p prop. If the 23p can spin the motor higher, that could potentially be bad? And they'd be the wrong prop anyway?

Slip is the real magic number. What engines do you have, 5000 rpm max??

Try them. A prop guy will tell you a Bravo 1 prop is -1 in pitch as far as they are concerned. So lets say your 26p is a 25p for true calculator. Your worked 23p with added cup, and labbed to reduce slip could out perform the 26p. But my guess is it will still also get you some more RPM.

sleev-les 07-22-2014 08:52 AM

I have carb'ed 502's (415hp). I have a spec sheet that came with them.. I could have misread and it was max HP at 5000. I just remembered a conversation with the seller and he mentioned that those props would be more top end than the 26p that are on there and when I saw a 23p marking, it just had me wondering. The 26's pull hard midrange, but was debating throwing the other ones on to try out.. I just am very novice in the prop world.

jbraun2828 07-22-2014 11:14 AM

I can't believe you can pull those 26's up to 5k with 415hp. I had 560hp with the same prop spinning to 5200. Overall a bravo 4 blade is the right prop for a bullet.

sleev-les 07-22-2014 11:29 AM


Originally Posted by jbraun2828 (Post 4157753)
I can't believe you can pull those 26's up to 5k with 415hp. I had 560hp with the same prop spinning to 5200. Overall a bravo 4 blade is the right prop for a bullet.

Don't know what to tell you on that one lol... It will go higher with a lighter load.. Maybe a little less than half fuel and 3 people. On my GPS, I clocked it at 73mph... The boat likes to move. Maybe the drive ratio? I've got 1.5 Bravos.. Can't you get a 1.3 as well? Thats why I sparked the conversation.. My clueless prop knowledge haha

bbladesprops 07-22-2014 12:37 PM

Efficiency remaining constant (same slip %), you would have to turn a 23 pitch prop 500 rpm faster than the 26 to run the same speed.
Therefore you would need to pull the 23 over 5500 rpm to gain speed over the 26.

Call us anytime and we can go into specifics for you.

Brett

pscoverher 07-24-2014 08:12 AM

i think so,Lower pitch will allow you to spin the engines to a higher RPM, thus more speed. thankshttp://goo.gl/XRZbT6

pstorti 07-24-2014 12:52 PM


Originally Posted by pscoverher (Post 4159072)
i think so,Lower pitch will allow you to spin the engines to a higher RPM, thus more speed. thankshttp://goo.gl/XRZbT6

think of prop pitch as the gears on a 10-speed bike, you can go the same speed in lots of different gears all that changes is how fast you pedal. You will go the fastest in the highest gear. I lower pitch prop will equate to higher RPM but unless the boat was overpropped to start you won't go faster.


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