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  1. #1
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    Evinrude prop help

    I have a 2 seater 1972 11 1/2 Cobra/baja boat with a 1972 Evinrude 50 hp short shaft motor. Heads milled 180psi, boyenson reed values I am running a 12 3/4 x 23p stainless Omc sst prop cupped. I am only turning it 5600 at 43-44 mph. I want to run a 23p prop 6000 rpm. What brand/model prop12 3/4 23p would allow me to reach the 6000 rpm. Motor is already set in the highest tilt position. It is 13 spline. Who makes a prop design that would solve this.
    Thanks

  2. #2
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    Your speed sounds pretty good for the fat electric shift gearcase on the early motors... Everyone wants more rpm unfortunately it takes more hp to turn the same pitch more rpm, a prop swap may get you a few mph and it may loose you a few mph... but 400rpm aint gonna be free. Hill propeller makes some nice cleaver/semi cleaver props for the 2 cylinders talk to them.
    Last edited by H2OPERF; 05-11-2021 at 06:13 PM.

  3. #3
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    Quote Originally Posted by H2OPERF View Post
    Your speed sound pretty good for the fat electric shift gearcase on the early motors... Everyone wants more rpm unfortunately it takes more hp to turn the same pitch more rpm, a prop swap may get you a mph and it may loose you a mph... but 400rpm aint gonn be free. Hill propeller makes some nice cleaver/semi cleaver props for the 2 cylinders talk to them.
    I really appreciate the tip I will contact them.
    Best Regards

  4. #4
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    Don't tilt the motor to the last bit. Raise the motor up. You will probably accomplish what you are after.
    Start at about 5" from the center of the prop shaft to the bottom of the boat, raise it till the prop can't grab the water or you start loosing water pressure. From there, if you want more, you start looking for a better prop like H20PERF said

  5. #5
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    Quote Originally Posted by sharpeye Mike View Post
    Don't tilt the motor to the last bit. Raise the motor up. You will probably accomplish what you are after.
    Start at about 5" from the center of the prop shaft to the bottom of the boat, raise it till the prop can't grab the water or you start loosing water pressure. From there, if you want more, you start looking for a better prop like H20PERF said
    1972 did not have power trim. So I run the motor on top notch 5th. I am looking for a better prop.

  6. #6
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    You'll obtain more speed by raising your motor than any other mods

  7. #7
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    Quote Originally Posted by sharpeye Mike View Post
    You'll obtain more speed by raising your motor than any other mods
    Thanks for your input I have it as high as it can go. I do experience some cavitation because it is so high. Basically looking for a 23p prop that is designed to enable me to achieve higher rpm and more top end.
    Best Regards

  8. #8
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    Click image for larger version. 

Name:	101_2225%20(2)[1].jpg 
Views:	14 
Size:	195.6 KB 
ID:	486973 This is my set up. Don't need much trim and I run 68 MPH with a warn out 56 cube Stinger

  9. #9
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    Quote Originally Posted by sharpeye Mike View Post
    Click image for larger version. 

Name:	101_2225%20(2)[1].jpg 
Views:	14 
Size:	195.6 KB 
ID:	486973 This is my set up. Don't need much trim and I run 68 MPH with a warn out 56 cube Stinger
    Tell me more boat size, horsepower, not sure what a 56 cube is. Also what about the prop no exhaust ring. Pitch and rpm at 68 mph. Sorry for all the questions
    Best Regards

  10. #10
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    The 56 cubic inch is the later version of 70 HP Johnson, It's mounted on an short shaft Johnson Stinger and the prop you see in the picture was made by Ron Hill. It's a Jeff Brown cleaver.
    My boat is a 13' single seat Delta padded Vee

  11. #11
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    Click image for larger version. 

Name:	IMG_2041.jpg 
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ID:	487000Click image for larger version. 

Name:	IMG_0961.jpg 
Views:	16 
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ID:	487001

    Here's a fly by

  12. #12
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    Quote Originally Posted by sharpeye Mike View Post
    Click image for larger version. 

Name:	IMG_2041.jpg 
Views:	13 
Size:	437.5 KB 
ID:	487000Click image for larger version. 

Name:	IMG_0961.jpg 
Views:	16 
Size:	428.4 KB 
ID:	487001

    Here's a fly by
    That's a great pic really gets out of the water bad ass!
    What pitch prop are you running and rpm? That 54 motor must put out 75-80 hp? Is it a 3 cylinder and what does the motor weigh. Would the guy that built your prop build me one?

  13. #13
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    Quote Originally Posted by sharpeye Mike View Post
    Click image for larger version. 

Name:	IMG_2041.jpg 
Views:	13 
Size:	437.5 KB 
ID:	487000Click image for larger version. 

Name:	IMG_0961.jpg 
Views:	16 
Size:	428.4 KB 
ID:	487001

    Here's a fly by
    That's a great pic really gets out of the water bad ass!
    What pitch prop are you running and rpm? That 54 motor must put out 75-80 hp? Is it a 3 cylinder and what does the motor weigh. Would the guy that built your prop build me one?

  14. #14
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    The complete motor weighs in at around 220-225 LBS since I installed a Yamaha Pro 50 trim and swivel bracket.
    The power head has only 120 LBS compression, even though the head are shaved 0.050"
    I've got another power head sitting on the bench with 135 LBS compression. If I ever get around to it, I will switch them.
    That prop is a 22" pitch but I can tell that it's pitch a bit higher than that cause I'm not spinning the RPM that I should. But having said that, my motor will last longer this way and I'm still getting great speed.

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