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  1. #41
    Platinum Member Platinum Member Wildman_grafix's Avatar
    Join Date
    Jun 2007
    Merritt Island, FL
    I would try swapping the props at this point. I can not think of anything in a Bravo drive train that can "Slip" without metal shavings (internal or external) everywhere and failing soon after.
    Just remember after you swap props, forward and reverse are backwards now. Maybe they are not matched, but it is a quick check.

    Do both engines run the same r.p.m. at WOT?

  2. #42
    Registered Platinum Member
    Join Date
    Jan 2010
    I currently have 3 blade 23 pitch stainless mirage props on both drives and to my knowledge both drives have the same gear ratios. I have closely inspected both props and neither has cracks, chips or dings.

    The port engine runs about 600 rpm higher than the starboard.
    Last edited by 336Formula; 02-03-2010 at 01:47 PM.

  3. #43
    Join Date
    Oct 2000
    Sussex, WI
    So do the motors eventually both turn 5000 rpm, 23's the 502's should push you to about 67 to 68 on the top end.

    If they eventually even out maybe you are just cavitating the props, at what rpm do you push the throttles forward, out of the hole or do you wait till the boat planes off and the props are hooked up, 3 blades will cavitate out of the hole pretty good with that boat.

  4. #44
    Charter Member#157 Charter Member MnFastBoat's Avatar
    My Boats:
    1999 Advantage 28' Cat
    Join Date
    Oct 2000
    Minneapolis, Mn, Usa
    Throttle linkage check?????
    You said the motors were removed for rebuild.
    Maybe the linkages are not set correctly?
    Carbs? Swap carbs and see if it follows?
    Vacuum leaks?? Sucking to much air higher in rpms??
    This Cat is trying to keep up with the Big Dogs

  5. #45
    My Boats:
    01' Nordic Heat, Whipple 540 with Holley EFI
    Join Date
    Jun 2009
    Kirkland, WA
    This will sound stupid, but check the plug wires (or broken plug). I got a boat back from the shop once and they had swapped the wires on the wrong plug. You would be surprised how good it runs like that, barely noticeable if your not ready for it. I chased all sorts of leads trying to figure that one out. Boat went 43, then 58 with the wires straightened out.

    Just a thought.

  6. #46
    Join Date
    Feb 2010
    Bristol, Indiana
    I would guess this is obvious, but when you had the overhauls, did you remove the motors, or did your technician do the entire deal? If they did it, make this their problem. If you took out the motors and had them rebuilt, then reinstalled them yourself, I guess would think that the problem is somewhere on the motors if everything else ran fine before the rebuilds...leading me to believe this fix might be something rather simple...but you will need to knock them off one at a time to determine the problem.

  7. #47
    My Boats:
    Formula 292 Fastech 2002 Scorpion engines
    Join Date
    Dec 2002
    Quote Originally Posted by US1 Fountain View Post
    Sounds like the port side is your problem, no speed loss and rpms raise faster.
    Try swapping the props.
    Possibly try getting on plain with just 1 motor. Not actually doing that, but making 1 side work harder, so if there is something slipping, you'd think it would show up then.
    I agree. It definitely sounds like the port side is not doing it's part of the work. Sounds like the starboard side is doing nearly all the work.
    May be there is less slip initially when you get on plane, from the port side and then it starts slipping after you are on plane.
    Otherwise I agree to let the port side do more work when getting on plane to verify that theory.

    Are the hubs of the props with rubber insert or solid ? If they are with rubber I would suspect a prop problem.
    Last edited by Phazar454Mag; 02-07-2010 at 05:29 AM.

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