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Discussion Starter #1
picked up a Scout Costa last week in really good shape. Has a three blade prop on it and it seems to be a good set up but its got alot of power on the top end and takes a little while to get up on plane.. WOT is around 36mph and I think around 5000 rpm. I would like to step up to a four blade and get into the 40mph range
 

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Some useful information about top speed with 4 blades

http://www.boattest.com/resources/view_news.aspx?newsid=3276

http://www.savvyboater.com/3-blade-prop-vs-4-blade-prop.aspx

http://www.marine-outboards.com/General_Info/choosing-propeller.htm
 

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picked up a Scout Costa last week in really good shape. Has a three blade prop on it and it seems to be a good set up but its got alot of power on the top end and takes a little while to get up on plane.. WOT is around 36mph and I think around 5000 rpm. I would like to step up to a four blade and get into the 40mph range
It's probably not going to happen, 4 blades are slower than 3 blades. In order to swing a 4 blade wheel you will have to have less pitch which will take away from your top end.

Rule of thumb less pitch better hole shot, more pitch more top end.

What HP motor and model do you have?
 

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its a Yamaha 90 2 stroke 2004 with 101 hours on it motor it self runs super I think I just may have to recup my prop.
 

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90 hp on an 800 lb hull should be doing better than 36 mph and 5000 rpm.
Something isn't right with the setup... :-?
 

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Discussion Starter #8
ran today and only got 30 knots out of it and it had alot more power on the top end I think I'm going to get the prop cupped and start again.
 

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Didnt see the need to redline it if i knew it was 10mph slow already the stock rated boat and motor package is set to run at 47mph
 

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Texas the reason to tun it up is to get a baseline for where you are at. If the motor would have turned say 6000 well then you need a bigger prop(more pitch) which will also be the reason your not getting the speed you want.

Cupping your prop isn't go to do anything for you.

What size prop are you running now?

Call Scout and ask them what is the recommened prop size they have awsome customer service.
 

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Discussion Starter #14
just looked at the yamaha bulletin for this boat they used a 13 1/4'' x 18 prop and the only marking on my prop is 16.... seems like its to small I'm going to order a 13 1/4'' x 18 and see what it does.
 

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Discussion Starter #15
http://www.yamahaoutboards.com/sites/default/files/bulletins/bulletin_2stroke_hpmidport_gyt3_sct-170costa-90tlr.pdf
 

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just looked at the yamaha bulletin for this boat they used a 13 1/4'' x 18 prop and the only marking on my prop is 16.... seems like its to small I'm going to order a 13 1/4'' x 18 and see what it does.
Is your prop SS or Aluminum? If it's SS take it to a local prop shop and tell them you want to make it an 18" it will be about 1/3 the cost of a new prop.
 

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Discussion Starter #17
just looked at the yamaha bulletin for this boat they used a 13 1/4'' x 18 prop and the only marking on my prop is 16.... seems like its to small I'm going to order a 13 1/4'' x 18 and see what it does.
Is your prop SS or Aluminum? If it's SS take it to a local prop shop and tell them you want to make it an 18" it will be about 1/3 the cost of a new prop.
It is and will do! I'm going to buy a cheap aluminum prop for a spare and test it before I get them to do my prop.
 
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