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Twin outdrives

  1. #15
    Bass Lake Dream'n "Flat" foot'n's Avatar
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    Quote Originally Posted by 4CE FED View Post
    Here's a few
    What are the big black rubber tubes coming up from the cav plates?
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  3. #16
    Scarab Racing Run_em_Hard's Avatar
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    Quote Originally Posted by "Flat" foot'n View Post
    What are the big black rubber tubes coming up from the cav plates?
    Those appear to be the same thing that you would see on a #6 drive. It helps large props get the air they need to get the boat on plane.

  4. #17
    Junior Member 31AOAZ's Avatar
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    the twin surface drive 'american offshore" is probably ron gibbs from bad attitude boats in parker. its actually a firehawk, but commonly confused with american offshore. i believe his setup was his own design. if you call him he might have what your looking for.

  5. #18
    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by Run_em_Hard View Post
    Those appear to be the same thing that you would see on a #6 drive. It helps large props get the air they need to get the boat on plane.
    Now I'm confused (easy to do)...but wouldn't air to the prop cause cavation and a slipping effect?
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  6. #19
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    IMCO has manufactured several of their "gear-splitters" for twin stern drive/single engine high performance applications. Randy Davis ran one of his 21-foot vee-bottom ski race boats with twin IMCO drives, a gear-splitter and a 1200 HP blown engine for power quite successfully. The twin drives with counter-rotating props make the boat super stable at 100+ mph. The only real disadvantage is the fact that you're pushing two lower units through the water instead of just one which reduces efficiency. The fact that two drives are sharing the torque, however, definitely improves the reliability factor. As for those "black tubes" on the back of the drives, those are "aerators" and they are there to induce propeller ventilation while getting on a plane. Big boats with very high pitch props need help to get the props spinning in order to build-up some engine rpm to get over-the-hump. Once the boat is at planing speeds, the props will take a clean bite and the aerators are no longer a factor to the performance.

  7. #20
    Member oknozelman's Avatar
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    I found some pics of the Firehawk on Arnesons facebook.






    I know blower belts are though but the belts will hold and a $10,000.00 or $15,000.00 Bravo type drive want? WTF
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  8. #21
    Member oknozelman's Avatar
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    IMCO has manufactured several of their "gear-splitters" for twin stern drive/single engine high performance applications. Randy Davis ran one of his 21-foot vee-bottom ski race boats with twin IMCO drives, a gear-splitter and a 1200 HP blown engine for power quite successfully. The twin drives with counter-rotating props make the boat super stable at 100+ mph. The only real disadvantage is the fact that you're pushing two lower units through the water instead of just one which reduces efficiency. The fact that two drives are sharing the torque, however, definitely improves the reliability factor. As for those "black tubes" on the back of the drives, those are "aerators" and they are there to induce propeller ventilation while getting on a plane. Big boats with very high pitch props need help to get the props spinning in order to build-up some engine rpm to get over-the-hump. Once the boat is at planing speeds, the props will take a clean bite and the aerators are no longer a factor to the performance.
    Has Imco ever made a gear spliter that will reach to the outside of a tunnel hull? Like my 26' Daytona And if you could get the driveline split do you think xr's, Imco's, or B-max drives could hold 1500 hp? Dividing the torqe between two drives, and I know it would be expensive but hell I can just put two blower belts on it!
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  9. #22
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    Default Evil twins


  10. #23
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    Whether IMCO could build a custom "gear-splittter" that accommodates a wider separation for a tunnel hull appication is something you need to take up with them (it would definitely be a custom one-off build) -- give them a call at (909) 592-6162 -- talk to Fred or Rick. For more info about the installation and maintenance of that type of set-up, Prime Marine is your place to go -- Mike Rameriz (909) 484-8338.

  11. #24
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    Somebody, maybe Randy Davis, raced a 42 single engine Fountain with two drives on it at the Catalina Ski Race a while back.

  12. #25
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    Default twin drives

    Not sure about that, Randys old Fountain was a 2 engine/2 drive set up. Nordic did a project boat with IMCO that was a single engine/twin drive set up though. Not sure if Randy was the principle then or not. Powerboat did an article on it.

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