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Twin Yamaha 1997 200HP Saltwater Series Carbureted fuel consumption excessive on 1

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  • Twin Yamaha 1997 200HP Saltwater Series Carbureted fuel consumption excessive on 1

    Twin 1997 Yamaha 200 Saltwater Series CARBURETED Both motors Rebuilt powerheads. same props. Both motors run great , both motors have a separate fuel tank. the port motor is burning a lot more fuel than the starboard. Last fill up was 43 gallons on starboard side, 55 gallons on port side. From an offshore trip so mostly high rpm 4000-4400. thats 28% *** . Both motors were rebuilt by marinas by the previous owner so all I have is what the receipts say. Neither motor seems to run rich, plugs look good in both motors. Seems like its getting worse. The fuel tanks are not leaking. I don't see any gas leaks or smell any. I keep them full so i can check mileage for the complete trip. Both tanks show full on the gauge and we fill it till it shuts the nozzle off.

    The oil consumption seems to be relative to the fuel consumption. I haven't measured the oil but always a lot more in the port side.

    Starboard - .040 oversize 250 hrs
    Port - Oversize but not sure how much 350 hrs

    Only thing i can think of is the jets in the carb are different? when you bore a powerhead I assume the jets would need to be changed so it isn't lean ? would be the same though not get worse.

    Tested today.
    Port motor 1.5 GPH 700 Rpm
    Starboard motor 1.2 GPH 700 Rpm

    Port motor 14.5 GPH 4000 Rpm
    Starboard motor 10.6 GPH 4000 Rpm

    Doesn't make sense to me.

  • #2
    Port is counter rotating LU?

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    • #3
      Originally posted by amahaork View Post
      Port is counter rotating LU?
      Yes port motor is left hand rotation starboard is right hand rotation. it has Yamaha SS 17M 15x17 props

      If its not raining when i get home today,
      Im Gonna check the fuel pumps for a hole in the diaphram, I replaced them last year.
      I recently installed Yamaha primer bulbs, New fuel line from the tank to the raycor filter/seporaters, I will replace the filters today also,

      What about the timing? Is it possible the timing is off and could cause this?

      Both motors idle a little low. about 600 in neutral, 500 in gear . in the water of course.

      Comment


      • #4
        I have same motor and happy with it. But timing has to be done precise by the book. So is carb idle adj. Only if you sure both adjusted the same to factory specs, you may compare fuel consumption. If you had hole in pump diaphragm, you would experience lean running, and only you may know that. Assuming compression, or leak, the same on both motors. Its for you to test

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