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New , classic mako owner__in South Miami

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  • New , classic mako owner__in South Miami

    1983 254, with 1993 twin yami 250's. I'll be buzzing around the board looking for answers to my 1001 questions. Good to be here and despite my project, a proud new owner of a 254 Classic Mako....

    I think I spun a hub the other night leaving Bayfront Marina... Attempting to plane, motor felt like she slipped and rpm went up with no forward momentum....any ideas?

    Also a quick question ... . I can't get her over 50 mph at 5000 rpm on both motors... Does that sound right? 500hp is overkill on that boat , and only 50mph? Not that I would go faster, but I'm thinking fuel economy as well. I thought it would cruise at about 45 and get about 20 mpg but ....I cruise at 3800 rpm , gives me 32mph at 19 gph.... To go 45 I have to be at 4700 rpm and its about 40 gph !!!

  • #2
    Welcome!

    How experienced of a boater are you?

    If you still get high rpm w/o propelling the boat, sounds like a spun hub. If it resumed normal operation after backing off and retrying, then it sounds like cavitation...trying to plane with the trim too high.

    I used to have a '70s 256 with twin 225s on it. Would do 48 knots @ 5000rpm....and that was with a full tower. The engines were bracketed, so that may make a diff...? do you have trim tabs? and how are you trimming the engines?

    20 mpg??? [:0]

    2 or 3 mpg is a high water mark many would love to reach.
    [br]DonK[br]Boca Raton, FL[br]1979 236IB: \'The Fish Tank\'[br]1979 Backcountry 18 \'Boner\'[br]<>< <>< <>< <>< ><> J[br]Redneck Troubleshooting:[br]1) If it moves, but ain\'t supposed to, use Duct Tape[br]2) If it don\'t move, but supposed to, use WD40[br]3) If that don\'t fix it, it\'s electrical![br]

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    • #3
      Thanks Don ! And thanks for the reply. I'm Not an expert by no means but I'd consider my self experienced to a degree but always learning something as well.

      I am leaning towards a spun hub as I had no propulsion after I retarde the throttle then advanced it ; as you mentioned. Out of the water with motor turned off but in gear , I can spin the prop with no resistance ... Unlike the other motor that has compression like resistance when I spin the prop.

      I made a typo with the 20 mpg haha, I ment 20 gph (gallons per hour) I installed the twinscan floscan gauges and I suppose with the math I was hoping for 2.25 mpg... But I am at about 1.3-1.6 . Which adds up over time.

      Maybe I'm trimming wrong, maybe I have too much boat in the water... This is my first REAL CC boat (last one was an Angler [xx(] and before that were 2 cabin cruisers an a 36 ft sailboat. Any advice would be appreciated . Awesome name of your vessel too, Fish Tank ! Real cool.

      Yes trim tabs as well..

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      • #4
        Definitely a hub...easy enough to replace yourself.

        Just to throw some gph numbers around for reference:

        My 236IB (330hp) @3200/24knt: 11gph; @5000/30knt: 17gph

        I average ~1.4-1.6 mpg on a light load and calm water when cruising.

        If memory serves, on my last boat (30' RyboRunner w/tower and 2x25 optimax) I was cruising at around 22gph (11 per engine) and HAM (haul ass mode) at 27gph. overall around 1.2 mpg.

        Sorry if you already know this, but to get your boat optimized:

        After your hole-shot and the boat is planing, trim your tabs for the sea-state....i.e. into a head sea, trim down to the point where it won't slam or porpoise. Trim bow up in a following sea.

        On calm water trim slightly down to have a better running attitude, but with as much hull out of the water as possible.

        After you have adjusted tabs for sea-state, then start trimming your motors up..this will increase the rpms. Not so far as to start cavitating, but it may be a lot more than you would expect.. You are looking to get the rpms into the top/most efficient part of the power curve.

        As you adjust the engine trim, you may need to put a touch of tab back on to compensate for the engine trim.

        In so many words: trim the boat with tabs, then trim the engines for rpm.
        [br]DonK[br]Boca Raton, FL[br]1979 236IB: \'The Fish Tank\'[br]1979 Backcountry 18 \'Boner\'[br]<>< <>< <>< <>< ><> J[br]Redneck Troubleshooting:[br]1) If it moves, but ain\'t supposed to, use Duct Tape[br]2) If it don\'t move, but supposed to, use WD40[br]3) If that don\'t fix it, it\'s electrical![br]

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        • #5
          Great info Don thanks. I'll try that... Once I get both trim motors back online. Trim tabs work great but now both trim motors are acting up. I replaced them both in December , I think the shop put on after market ones at OEM price. Doesn't make sense they would act up already. Port side runs and does little or nothing like needs to be bled. Tried it but manual valve won't budge. I can lift manually after someone pressed uptrim and I can lift it but I need a 6x6 wood to hold it up. Trims down fairly well. The other one works after getting bashed with a hammer haha. Also manual valve won't turn on that one either arggg.

          I guess my fuel numbers are not that far off. I guess I thought better sense i am over powered, but it is what it is. I told someone I had 250's and he was "like whoa that thing will do 70 mph . " when I got to 50 I was disappointed that's all she had. But I'll try your trimming advice and see what that will do, not that I really want to do 70 mph anyways.

          Thanks again for the time.

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