Need Help with holeshot on 22 scarab.
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Need Help with holeshot on 22 scarab.

  1. #1
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    Default Need Help with holeshot on 22 scarab.

    Hi,
    I have a 22' Scarab and just wanted to see if I can get some info and a direction to go. A little about the boat, It has a 454bbc merc motor in it, we are in denver so a little altitude out here and it has a 24 pitch prop. with a brovo I outdrive.

    Problem: The holeshot stinks I can barely plane. I know the pitch is prob too big for out here but I want to see if that is really the case or if there is something else that can be done. I like the speed it has at full throttle I hit about 56mph with 4 people and turning 4200 rpm. Thats why I want to see if there is something else I can do it is only hitting 4200 rpm. On takeoff the motor is at 3000 rpm till it planes out.

    If I go to a smaller pitch and get the motor running around 4800 rpm will that make up for the smaller pitch size? I just think 4200 rpm is quite low. any info would help because im a little new to boating.
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  3. #2
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    At 4200 wot the eng. is laboring. Prop boat for 4800 with normal load. Meaning you need to lower prop pitch. A 21-22p would be in order.
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    Is that speed on GPS?
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  6. #4
    Senior Member Dave Strong's Avatar
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    Drop to a 22" pitch same prop and speed should be close to the same, little better if your lucky and the holeshot should improve. Try to stick to the same prop for your first changes then after may find a different prop that does a better job at every thing.

    Dave
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  7. #5
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    If interested I have a 4 blade stainless 22 pitch bravo 1 prop I am looking to swap for a 24 pitch stainless 15" four blade.
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    Yeah Its on gps im going to take it out again to make sure and im going to advance the timing a little it was at sea level. Now im 5000 ft up which stinks. It is a ss prop. Im going to tune it up run it again and make sure all my info is correct but sounds like just a smaller pitch to get the motor running where it needs to be. Isnt it 300-400 rpm added in each pitch drop ie 24 to 23 will give me 300 or so rpm?

    I think I might want to stick to a 3 blade prop. and keep this one as a back up and incase i go to vegas with it anythime soon. thank you though.
    Last edited by GregGallegos; 07-20-2010 at 10:00 AM.
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  9. #7
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    Quote Originally Posted by GregGallegos View Post
    Yeah Its on gps im going to take it out again to make sure and im going to advance the timing a little it was at sea level. Now im 5000 ft up which stinks. It is a ss prop. Im going to tune it up run it again and make sure all my info is correct but sounds like just a smaller pitch to get the motor running where it needs to be. Isnt it 300-400 rpm added in each pitch drop ie 24 to 23 will give me 300 or so rpm?

    I think I might want to stick to a 3 blade prop. and keep this one as a back up and incase i go to vegas with it anythime soon. thank you though.
    If you have a 1.5 drive ratio, your current slip is around 12%, which is fine for a v-bottom.

    If you can spin a 22 to 4,800 and keep your same slip, by my calculations, you'll be at 58MPH.

    A 3 blade 22 on a 22' boat may work well- good luck.
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  10. #8
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    Thank you, nothing beats math so 58 will have to do now till I get motor work done. Thanks ill look into maybe a 22 pitch get a hair mor out of it. Thank you all for your help.
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    Keep an eye on your engine and oil temp for signs of overloading the engine, nothing will bring on early failure like over propping. For long engine life, if you have a stock Merc motor, you should try to prop it to mfg's max RPM and just accept the top speed limitation. If you want to go faster, buy more HP. With the 24 prop it's like you are in 6th gear going up a steep hill when you really want to be in 3rd or 4th. You might even gain some speed and improve the holeshot by letting your rpm's get higher up into the powerband by going to a smaller prop.

    I am going through a similar experience with my boat, I started with a 23 3 blade that would only let me rev up to 4400 and now I am trying a 19 5 blade next week to try to improve slip. A 20 4 blade gave me 5400 rpm. All along the gps speed has stayed about the same: mid-50's with 20% slip. I have a heavy boat with a deep, draggy lower unit that takes a lot of hp to go over 60, so I am trying to improve efficiency to keep the existing top speed, but improve cruise performance (mpg).

    You should also make sure your boat is tuned for your altitude including any carb adjustments needed as well as timing changes. There's no sense spending money on props if it all goes out the window once you get a tune-up, especially if your boat is from somewhere else and set-up for a lower level.
    Last edited by Westfield 11; 07-21-2010 at 10:51 AM.
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