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  • Fuel system

    Just bought a 79 25" mako and it has 2 fuel tanks can anyone tell me how much each tank holds? and what is my fuel burn going to be with a 1990 johnson 225, we disconected the oil injection and are mixing oil straight to the tank?, can't figure out where the forward tank is? I think that the aft tank is under the rockett launcher. I went to the owners manual links for 70's mako 25 and that manual looks nothing like what I have got? any help
    Time Flies 79 25\' mako Marathon Florida

  • #2
    There are several 25 owners on this board, Hang tight and you will be overwelmed with good info, BTW, welcome aboard, and can you also include your location in you signature line so we know where to send you for parts and such. heck who knows we might be neighbors!! dave
    [br]1994 Mako 215 Dual console Optimax 225[br]1978 Mako 19 with 90hp johnson[br]1996 Mako 22[br]1982 Mako 171 Angler 135 Black Max Mercury[br]1987 21b 225 Yamaha[br]1974 23 inboard Gusto gone.[br]1979m21 225johnson \"blue dolphin\" bought off this board and restored [br]with everyone\'s help!!Gone but not Forgotten....[br]1979 20 Mako 115 Suzuki gone[br]1977 19 Mako 115 Johnson gone[br]1976 23 Mako twin 140 Johnsons gone[br]1983 224 with closed transom and bracket[br]And 162 SOB (some other boats)[br]Venice Florida, Traverse city Mi.

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    • #3
      quote:


      Orginally posted by Time Flies:

      ...what is my fuel burn going to be with a 1990 johnson 225, we disconected the oil injection and are mixing oil straight to the tank...



      My father's boat (1978 Whaler Revenge 21') has a Johnson 225 ~1991. For a round trip to our duck camp (inland/marsh waters with heavy load), we usually burn ~14 - 16 gallons (Premium unleaded). Trip mileage is around 32.5miles. This would yield about 2.16mi/ga.

      Good move on removing the oiler. These will eventually fail. However, some people simply replace them with new. The only problem with complete removal is the damn buzzer will go off when under a heavy load at high RPM's. You have to bypass the oiler sensor harness to stop this.

      -Pat
      18ft MonArk tri-hull: 140HP Mercruiser Alpha One - still in pieces...to be continued[br](I know it\'s not a Mako, but hey, its mine!)[br] Time\'s fun when you\'re having flies![br]president/hostmaster:[br]P.Ring Technologies[br]Cornerstone IT, LLC[br]LOUISIANA WEB HOST, LLC.[br]CompTIA Certified Professional A+/Network+ // Microsoft Registered Partner

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      • #4
        the '76-'77 Mako CC had the 86 gal tank stock and and optional 36 gal tank. The larger tank (aft) is under you hatch below the helm, the smaller tank is forward of the larger tank.
        Artie Sutherland[br]Rude Attitude -\'76 Mako 25 CC. - SOLD[br]1976 Mako 21[br]2002 Yellowfin 31 - 300 hp Suzukis[br]Gulf Coast, Mississippi[br]

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        • #5
          So when you are filling the forward port on the port side, that is the forward tank right the reason I as the fuel guages may be marked back wards? also the fuel sender under the rocketlauncher is that the sender for the aft tank?
          Time Flies 79 25\' mako Marathon Florida

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          • #6
            Yes. Yes. Yes......

            Of the stock 25'ers from '76-'79 with the twin tank setup, I've never seen an access hatch to the forward small tank. The sending unit behind the console will be your aft tank. The forward tank sending unit will need a hatch cut for access if necessary.

            Do you have a valving system to select which tank you use. Is it at the filter?

            Not sure about the fuel gauges being backwards. Guess that has to do with how you look at it. In the morning the guage on top might swap ends to the guage on bottom after the icechest is empty... [88][88][]
            Artie Sutherland[br]Rude Attitude -\'76 Mako 25 CC. - SOLD[br]1976 Mako 21[br]2002 Yellowfin 31 - 300 hp Suzukis[br]Gulf Coast, Mississippi[br]

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            • #7
              ok just as i thought valves to switch the tanks are under the center console and the fuel water seperator is in the back before the engine, the aft tank guage is reading full? I know it is not yet if it is the 78 gal and the forwad tank guage is half tank as I have only been bringing her 6 gal juggs from the gas station and mixing, the forward tank is full and venting overboard oops!
              Time Flies 79 25\' mako Marathon Florida

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