Props , Do these #s make sence - Moderated Discussion Areas

  ContinuousWave
  Whaler
  Moderated Discussion Areas
  ContinuousWave: Whaler Performance
  Props , Do these #s make sence

search | FAQ | profile | register | author help

Author Topic:   Props , Do these #s make sence

rves posted 05-15-2005 10:01 PM ET (US)
1988 22wtwd twin yamaha 150s I have been testing props as you may have read !
Today I tried a pair of 13" maybe a little less no # no brand marked ss 15" that is all
I am in love, the boat does everything I could want and more right up to 45 gps mph @ 5000 rpm
what is confusing me is the single engine performance ! Its great I get 47-4800 on one engine alone (yet only 5000 on 2 ?) & it plains quickly
it tops out at 33-35mph on just one and it will stay on plane down to 2900 rpms on just one engine !
By far the smoothest props I have tested on this boat and they are dinged up a little to boot!
Do these single engine performance # make sence ? the performance is so much better than the high dollar large diameter props I have tested and the 4 blades both of which had trouble running single and even my yamaha props that were kind of small were not super like these ! Every time I drop diameter on this boat it handles better & better
I want to try 12.250" next If I can locate a pair ! T

jimh posted 05-15-2005 11:21 PM ET (US)
Theory tells us speed is a function of horsepower to the 0.5 power. If you increase horsepower by a factor of 2, speed increases by a factor of ( 2^0.5 or ) 1.4.
Your data:
Speed with one engine = 33 MPH
Speed with two engine = 45 MPH (twice the horsepower)
45/33 = 1.36 <--> 1.4 predicted by theory.
Your results are in very close agreement with theory.

Hop to:

Contact Us | RETURN to ContinuousWave Top Page

Powered by: Ultimate Bulletin Board, Freeware Version 2000
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.

Author	Topic: Props , Do these #s make sence
rves	posted 05-15-2005 10:01 PM ET (US) 1988 22wtwd twin yamaha 150s I have been testing props as you may have read ! Today I tried a pair of 13" maybe a little less no # no brand marked ss 15" that is all I am in love, the boat does everything I could want and more right up to 45 gps mph @ 5000 rpm what is confusing me is the single engine performance ! Its great I get 47-4800 on one engine alone (yet only 5000 on 2 ?) & it plains quickly it tops out at 33-35mph on just one and it will stay on plane down to 2900 rpms on just one engine ! By far the smoothest props I have tested on this boat and they are dinged up a little to boot! Do these single engine performance # make sence ? the performance is so much better than the high dollar large diameter props I have tested and the 4 blades both of which had trouble running single and even my yamaha props that were kind of small were not super like these ! Every time I drop diameter on this boat it handles better & better I want to try 12.250" next If I can locate a pair ! T
jimh	posted 05-15-2005 11:21 PM ET (US) Theory tells us speed is a function of horsepower to the 0.5 power. If you increase horsepower by a factor of 2, speed increases by a factor of ( 2^0.5 or ) 1.4. Your data: Speed with one engine = 33 MPH Speed with two engine = 45 MPH (twice the horsepower) 45/33 = 1.36 <--> 1.4 predicted by theory. Your results are in very close agreement with theory.