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  1. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    OK I think I've solved the issue! After checking compression (145-144-149-145) and getting fresh ethanol free gas I was playing with the linkage on the carbs while running. I noticed the intake side of the linkage would not open till FULL THROTTLE. So I held that linkage open while accelerating...
  2. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    Where I'm at and none of this has fixed the problem: all the carbs have been refreshed with new floats, needles, gaskets and seals new spark plug coils new fuel pump Seafoam intake treatment Basically the cylinders have black carbon build up and the motor runs rough when increasing...
  3. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    No luck, the choke is not the issue, unplugging the choke solenoid and visually inspecting it not operating during running and the problem persists
  4. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    thanks for this, I just checked the solenoid when starting and the choke linkage moves with start up, I'm going to unplug the solenoid and test run this afternoon, I may be dealing with an "always on" solenoid interesting a few months back the spring mechanism in the key stoped working, pushing...
  5. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

  6. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    confident from the parts drawings and manual search is does not have an automatic choke system? the only reference to "choke" is the linkage on the carbs, this all appears to be operating similarly to how it has been the carburetor has been gone through - new floats/needles and gaskets new fuel...
  7. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    ran the motor with the cowling off, none of the linkage attached to the prime starter or solenoid moved (see pic of carb breakdown, same problem persists not fuel injected
  8. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    not 100% clear on actual function beyond what the parts are titled there is a primer starter that extends and opens the front carb choke plate with linkage there is a solenoid above that the extends with the same linkage, its unclear to me how that works? likely tied to the choke and appears to...
  9. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    Confirmed Prime Starter is operating as expected.
  10. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    Yes, all cylinders show black carbon build up on the plugs
  11. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    You are correct, there is a solenoid and prime starter unit and connecting linkage to the four carbs. I'm going to pull off the prime starter and test it as the manual shows. https://www.manualslib.com/manual/909046/Yamaha-F50a.html?page=119#manual this is the main thing, the motor was running...
  12. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    new thermostat replaced last year gonna try a few other things before I remove the head...
  13. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    Yes all plugs show signs of over rich as mentioned its a mechanical fuel pump that I replaced with a new one
  14. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    got back into the carbs, looks like the float is out of spec in the closed position by 1/16" replacing with new floats, also the o-ring for the plug on the main jet was cracked and old replacing those as well
  15. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    spark is good, replaced coil packs for plugs and problem did not go away valve clearance is next I suppose...
  16. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    Cleaned carbs, no issues with floats and no float pin wear. Adjusted the fuel pilot screw all the way in to 1/2 turn out limiting fuel from the carb, same problem, running rough when accelerating. Replaced the coils packs for the spark plugs, same problem no improvement.
  17. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    Copy that, going to adjust the pilot screws down to limit fuel flow.
  18. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    Compression test 150 130 150 140 No water in the oil Spark plugs have black chucky carbon build up will check spark and replace coils by end of week If I check valve clearance do I need to replace the valve cover gasket?
  19. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    Problem is persisting. Balanced the air/fuel ratio on carbs per manual and it runs great on the muffs. The second the motor is in the water it runs really rough and gets worse with higher acceleration. Could it be bad coils?
  20. JLarimar

    4 stroke 50hp 1997 Yamaha outboard black smoke rough runnning

    All the floats and float valves are in good shape. Changing out all the gaskets for good measure many were very flat.
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