Thread: Drive height

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    Drive height
    #1
    What are you guys running for drive height on your BT's? Anyone know the approximate depth they are below the running surface directly in front of the drives? Any help would be greatly appreciated.
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    #2
    Founding Member / Super Moderator Ratickle's Avatar
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    Are you still running at this depth?

    Quote Originally Posted by splashandburn View Post
    Here's a photo. I did measure it again from the bottom of the boat directly in front of each drive to the centerline of the prop and its actually closer to 6" below that point.

    Attachment 75968
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    #3
    Yes. I never got the boat dialed in last year - ended up blowing a motor @ less than 30 hours. Both motors reworked (again) and pushing even more lower now. I'm getting extremely high slip numbers running a 32P Bravo I prop. Just received new drive couplings to put the drives back to stock depth which looks to be close to 4" below the running surface.
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    #4
    Founding Member / Super Moderator Ratickle's Avatar
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    Don't know why the photo didn't come across in the quote. Here it is:

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    #5
    Yup that's it with the spacers installed. Removed now and IMCO SCX uppers installed.
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    #6
    Charter Member Coolerman's Avatar
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    Ever tried 5 blades? Seen several 460's that like, not sure what 5 blades they were.
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    #7
    I haven't. I do think the boat needs bow lift though I can almost feel it plowing at speed. I'm wondering if the spacers were pushing the bow down?
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    #8
    Charter Member Coolerman's Avatar
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    Spacing the drives down usually leverage the bow higher.
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    #9
    Registered endeavor1's Avatar
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    My 02 46 with KE675s or as dyno proven 699s ran BMAX drives with standard XR lowers with Hydro P5X props. Boat handled good, carried the nose and was enjoyable with minimal tab. Same boat with 4 blades became an absolute turkey. Try no spacers and P5X props.

    Btw, my first 43 had -2 lowers and when I put standards on it it slowed and completely changed for the worse its handling. John P with No-Comp (trip 850) 46 saw gains after we discussed -2 vs std lowers.

    Short drives/more prop... Have fun
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    #10
    Hmmm....not sure what I've got going on then. I was thinking that having the drives that deep was increasing my slip numbers. I'm running close to 30% slip @ WOT.
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    #11
    New motors dynoed at 890 hp. Boat seems to hit a wall @ 74 mph. How is it getting on plane with -2? I seems to really blow out the 32P props WITH the spacers installed - can't imagine what it'd be like with 4" less in the water
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    #12
    Charter Member Coolerman's Avatar
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    Are you running the props that came on the boat, or do you know the history on the props before you got them? Or has anyone worked on them?
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    #13
    Founding Member / Super Moderator Ratickle's Avatar
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    When I look at the tab locations on your photo I'm confused. Are they mounted within a half inch of the bottom? And is the port lower than the starboard, or is that a visual mirage?
    Getting bad advice is unfortunate, taking bad advice is a Serious matter!!
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    #14
    Registered endeavor1's Avatar
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    4 blades on my 46 blew out, my current 43 did too until b blades worked them. 5 blades on my 46 hooked up and rolled on plane no issues.

    If I had 890hp and hit 74 I'd be crying. I hit that Friday night late under the community bridge @ Loto with my catastrophe of power I call engines...fWIW, when my engines were procharged they were odd to understand the power and along with finicky. 775hp per dyno.

    Call me if I can be of any help to discuss my setups.
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    #15
    Founding Member / Super Moderator Ratickle's Avatar
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    Also, with your spacers installed, I have to believe the cavitation plate was running in the water even at WOT. They were just too low.

    Typically the water starts to rise to its normal level as soon as it leaves the transom. Your cavitation plates appear to be lower than the bottom of the boat in the photo. I think they were displacing water and aerating the water to the prop also.
    Getting bad advice is unfortunate, taking bad advice is a Serious matter!!
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    #16
    Quote Originally Posted by Coolerman View Post
    Are you running the props that came on the boat, or do you know the history on the props before you got them? Or has anyone worked on them?
    I have a set of stock Bravo I 28P props that I know are untouched and a set of Bravo I 32's that were Mercy labbed.
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    #17
    Quote Originally Posted by Ratickle View Post
    When I look at the tab locations on your photo I'm confused. Are they mounted within a half inch of the bottom? And is the port lower than the starboard, or is that a visual mirage?
    Yes both are close to 1/2" down and at the same level. Must just be the pictures angle. .
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    #18
    Registered endeavor1's Avatar
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    My 43 with PC'd motors ran 32 b1 props as info.
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    #19
    Quote Originally Posted by endeavor1 View Post
    My 43 with PC'd motors ran 32 b1 props as info.
    The 32's seem to be the right size as I spun them to 5100 rpm but it seemed to be dragging. I could actually feel (and see) the speed increase if I turned the boat slightly. The water was dead flat though.
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    #20
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    Saxman... Why are these boats turkeys to dial in?
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