Prop Ideas
10-04-2005, 12:47 PM
#11
Re: Prop Ideas
I agree wholeheartedly with Throttleup on the idea that it would be very difficult to get 600 hp at only 5100 rpm from N/A 496. That's why I specified a 5400 RPM power peak, and Supercharging in my second guesstimate. I have a N/A 540, which has to run to 5400 to make over 600 hp.
At any rate, unless your motors come out with the power curves we've thrown around, you won't get what these predictions show. I would expect that you'll need more RPM to get the power you want, which means less pitch like Corbra Marty says. When you put in more RPM, you get worse efficiency through the gears in the drive unit due to viscous oil drag, and you actually go slower than with the same amount of power occuring at lower RPM (and a proper setup.)
Not to discredit any engine builder or aftermarket supplier, but do not assume that any specific modification will yield X amount of power and torque on your engines until you have witnessed on the dyno what your engines can do on any given day, and not the best of a series of runs achieved by tweaking and tweaking.
Prediction tools such as the one I have written are "stupid", meaning that they will run any scenario you put into them. Getting correct, usable results is totally dependent on gathering the correct information in the first place to use as inputs. That being said, please let us know how your motors turn out, and how the boat ends up running!!
At any rate, unless your motors come out with the power curves we've thrown around, you won't get what these predictions show. I would expect that you'll need more RPM to get the power you want, which means less pitch like Corbra Marty says. When you put in more RPM, you get worse efficiency through the gears in the drive unit due to viscous oil drag, and you actually go slower than with the same amount of power occuring at lower RPM (and a proper setup.)
Not to discredit any engine builder or aftermarket supplier, but do not assume that any specific modification will yield X amount of power and torque on your engines until you have witnessed on the dyno what your engines can do on any given day, and not the best of a series of runs achieved by tweaking and tweaking.
Prediction tools such as the one I have written are "stupid", meaning that they will run any scenario you put into them. Getting correct, usable results is totally dependent on gathering the correct information in the first place to use as inputs. That being said, please let us know how your motors turn out, and how the boat ends up running!!
10-04-2005, 02:00 PM
#12
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Re: Prop Ideas
Ray,
Those are great numbers!
One consideration; with boats that are relatively light the torque can control the boat, especially with tal pitch props That's why those little 900lb outboard boats with 400 hp have to turn 9,000-10,000 rpm. They make lots of HP but little torque.
Of course the bigger and heavier the boat the less effect the torque has on the boat.
Ray and blanaic keep us posted on this project I am interested to find out how it works out. blaniac, If you need some test props for your project give us a call, we have the Bravo's in test props all the way to 34.
Matt
Those are great numbers!
One consideration; with boats that are relatively light the torque can control the boat, especially with tal pitch props That's why those little 900lb outboard boats with 400 hp have to turn 9,000-10,000 rpm. They make lots of HP but little torque.
Of course the bigger and heavier the boat the less effect the torque has on the boat.
Ray and blanaic keep us posted on this project I am interested to find out how it works out. blaniac, If you need some test props for your project give us a call, we have the Bravo's in test props all the way to 34.
Matt
10-04-2005, 03:59 PM
#14
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Re: Prop Ideas
Originally Posted by throttleup
Ray,
Those are great numbers!
One consideration; with boats that are relatively light the torque can control the boat, especially with tal pitch props That's why those little 900lb outboard boats with 400 hp have to turn 9,000-10,000 rpm. They make lots of HP but little torque.
Of course the bigger and heavier the boat the less effect the torque has on the boat.
Ray and blanaic keep us posted on this project I am interested to find out how it works out. blaniac, If you need some test props for your project give us a call, we have the Bravo's in test props all the way to 34.
Matt
Those are great numbers!
One consideration; with boats that are relatively light the torque can control the boat, especially with tal pitch props That's why those little 900lb outboard boats with 400 hp have to turn 9,000-10,000 rpm. They make lots of HP but little torque.
Of course the bigger and heavier the boat the less effect the torque has on the boat.
Ray and blanaic keep us posted on this project I am interested to find out how it works out. blaniac, If you need some test props for your project give us a call, we have the Bravo's in test props all the way to 34.
Matt
Want to trace a pair of labbed 26's for a pair of labbed 30's ?
I also have a pair of labbed 34's that I bought for the project that sound like they are going to be useless for my needs.
10-04-2005, 04:24 PM
#15
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Re: Prop Ideas
Before you buy, sell or trade props I would try the props you have now or can get your hands on. Get as many numbers as you can with as many different props you can get your hands on. We also have 5 blade props as test props you can try as well. After you get as many numbers as you can then you can make the best decision as to what worked best for your boat and your goals.
No need to have a garage full of props that you can't use.
Matt
No need to have a garage full of props that you can't use.
Matt
10-04-2005, 04:39 PM
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Re: Prop Ideas
Originally Posted by throttleup
Before you buy, sell or trade props I would try the props you have now or can get your hands on. Get as many numbers as you can with as many different props you can get your hands on. We also have 5 blade props as test props you can try as well. After you get as many numbers as you can then you can make the best decision as to what worked best for your boat and your goals.
No need to have a garage full of props that you can't use.
Matt
No need to have a garage full of props that you can't use.
Matt
Any ideas ?
10-04-2005, 05:00 PM
#17
Re: Prop Ideas
It all depends on how you boat. If you run WOT 90% of the time with 2 passengers and light fuel in the 70-85mph range then the 30" are the choice. If you run 10%WOT with 4-6 passengers and full of fuel and beer in the 50-75mph then the 28" will have incredible acceleration and mid range pull. Better yet order a set of prop holders from Trick and have them both. I can't wait to hear your results.
10-04-2005, 05:47 PM
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Re: Prop Ideas
Originally Posted by cobra marty
It all depends on how you boat. If you run WOT 90% of the time with 2 passengers and light fuel in the 70-85mph range then the 30" are the choice. If you run 10%WOT with 4-6 passengers and full of fuel and beer in the 50-75mph then the 28" will have incredible acceleration and mid range pull. Better yet order a set of prop holders from Trick and have them both. I can't wait to hear your results.
