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Top End Speed

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bighawkeye

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I just purchased a 2575 with a Yamaha 250 SHO motor and cant get the boat to exceed 41 MPH despite the performance bulletin stating 44 with the same set up? Also my stainless 15.5 * 17 propeller seems to slip easily in hard turns. Any ideas or comments would be greatly appreciated?
 
Many factors can play into the elusive 3 mph difference. Water conditions, wind speed, altitude, cargo weight, engine trim, to name just a few. Now, for the factors you can control. Are you trying to obtain this speed with proper engine trim? How is your cargo weight and placement of said cargo? This factor can be crucial. Do you have the top up or down for your speed check test?

As for the prop washing out in turns. I believe the term is called propeller ventilation. For a short discussion on this, go to this link: http://boatpropellers.iboats.com/propeller-tutorials/ventilation/. In short, it is air being sucked into the propeller during a tight turn causing a raise in rpm's and momentary loss of some power.

I hope some of this information helps. Good luck.

Oh, one other thing on the speed test. Are you using the boats speedometer, or a gps? Boat speedometers have a reputation of not being accurate.

And last but not least, welcome to the forum.
 
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The first thing I would check is the mounting of motor. Is your motor mounted on the bottom hole? If not then you may need to have it moved down. Also the SHO motors are a 20 inch shaft not a 25" like the reg Yamahas. I beleive you have to order the boat with a 20" transon to run that motor. Hopefully you have the right transon and can move the motor down.
 
Thank you for the feedback. I may be switching to a stainless SOLAS propeller that is designed specifically for Yamaha outboards. Thanks again.

quote name='amr7333' timestamp='1310559398' post='2508']

Many factors can play into the elusive 3 mph difference. Water conditions, wind speed, altitude, cargo weight, engine trim, to name just a few. Now, for the factors you can control. Are you trying to obtain this speed with proper engine trim? How is your cargo weight and placement of said cargo? This factor can be crucial. Do you have the top up or down for your speed check test?

As for the prop washing out in turns. I believe the term is called propeller ventilation. For a short discussion on this, go to this link: http://boatpropellers.iboats.com/propeller-tutorials/ventilation/. In short, it is air being sucked into the propeller during a tight turn causing a raise in rpm's and momentary loss of some power.

I hope some of this information helps. Good luck.

Oh, one other thing on the speed test. Are you using the boats speedometer, or a gps? Boat speedometers have a reputation of not being accurate.

And last but not least, welcome to the forum.
 
Hey Bighawk,

I have the same the same Yamaha 250 SHO too so I am quite interested in your situation. Our boat is a 2275 RCW so my weight is a little lower than yours. Our boat came with an aluminum prop and I am very interested to see if the stainless will help with performance. Both the top speed and ventilation. Look forward to your results.
 
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