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  1. #1
    born riding's Avatar
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    max CFM required by engine

    does anyone know what the max CFM for this motor is? I got the formulas to do it, but I wanted to compare results, or see if anyone already knows the answer to it. I will run my numbers and post them tonight.


  2. #2
    250 HP=333.62 cfm or 23.02 lbs per minute

  3. #3
    Silence! I Keel You! earthshaker's Avatar
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    SC moves 2 liters every revolution.

  4. #4
    born riding's Avatar
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    fans

    i have 2 bilge fans, 3 in, 145 cfm each. both in front ducts. i guess this is limiting at full speed.

  5. #5
    Formerly Ultra250 TN Aquaholic6801's Avatar
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  6. #6
    Silence! I Keel You! earthshaker's Avatar
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    Yep, and also more than likely overtaxing your electrical system. If using stock inlets, you're even restricting further.

    Use one fan in the rear on stock electrical system.

    Quote Originally Posted by born riding View Post
    i have 2 bilge fans, 3 in, 145 cfm each. both in front ducts. i guess this is limiting at full speed.

  7. #7
    Quote Originally Posted by born riding View Post
    i have 2 bilge fans, 3 in, 145 cfm each. both in front ducts. i guess this is limiting at full speed.
    Why would it limit top speed? In stock form you have 4 air inlets right? If the engine uses 333.62 cfm that means it pulls 83.41 cfm through each inlet when at WOT. If you have 290 cfm going into the hull through the fans the engine will just use all that air and only have to pull 42.62 cfm through the other 2 inlets. Thats only 21.81 cfm in each inlet. thats a whole lot less restriction than the stock set up. Plus anything less than full throttle the excess air in the hull will just blow out the back taking heat with it. And with 2 fans pushing into the hull you will pressurize the hull slightly and that will help"push" the air into the engine
    If you position 1 fan on the rear to draw heat out of the hull that would be fine at low speed and part throttle cruising,but at WOT the fan will being working against the engine because the engine will be trying to draw air into the hull through 3 inlets while the fan pushes it out of the fourth. that means the engine will have to pull its 333.62 through 3 inlets,or 111.20 through each of the 3 inlets. Thats 27.70 cfm more than stock.

  8. #8
    Banned User
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    Could some one smarter than me please tell me how much air a 2 stroke 1500 cc engine would need.

  9. #9
    Quote Originally Posted by Rocketman View Post
    Could some one smarter than me please tell me how much air a 2 stroke 1500 cc engine would need.
    how much HP does it make?

  10. #10
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    Kerry,

    When you going to start working on the 250's?

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