1985 150 blackmax running rough at differant rpms

Discussion in 'Bubba's Outboards' started by Nite, Aug 6, 2008.

  1. Nite

    Nite New Member

    Messages:
    1
    State:
    mass
    I just bought a 1985 150 merc blackmax.
    The motor runs a little rough at different rpms and speeds up and slows down without touching the throttle.
    The boat rips out of the hole and jumps to a plain but at full throttle the motor breaks up if i back down a little it clears up back down a little more it breaks up back down a little more clears up again.
    It acts the same way increasing the throttle at a slow rate.
    I have replaced the plugs, rebuilt the carbs and adjusted the timing
    Im not sure where to look next anyone have a clue?
     
  2. DoubleG

    DoubleG New Member

    Messages:
    77
    State:
    Kentucky
    Have you checked the fire? A buddy of mine has a 200 blackmax w/close to the same problems but mostly high rpm. His problem was the switchbox or powerpack to the even cyl's. Local repair shop let him try a powerpack to check if that was the problem. It ran like a new engine. I think a new one was $180.00. On the plus side, easy to change....