Shutter during throttle up Normal?

Discussion in 'Bubba's Outboards' started by my4x4awd, Apr 28, 2007.

  1. my4x4awd

    my4x4awd New Member

    Messages:
    105
    State:
    TN
    I rebuilt the 1978 Evinrude 70hp last September and it has been running great. Since the last engine I had was a 1960 model, Im not sure what to expect. I soaked and rebuilt the carbs and syncronized them per the book. The engine idles ok maybe some would say a little rough, never dies and starts easy hot or cold. It runs full throttle fine no missing popping etc.. How smooth should this engine be? Should it really purr or being 2 cycle is there some roughness. It has had this issue since I rebuit it. If i give it just a litte throttle running 10mph it will shake a little bit. It seems it only does this when slightly under load. Any ideas or is this nothing to worry about.
     
  2. Thommo

    Thommo New Member

    Messages:
    19
    State:
    Tasmania, Australia
    I think it is endemic of th 2 stroke. My 2005 30 hp 2 stroke Yamaha shudders and vibrates at low speed, seems to be running on 2 cylinders; like yours starts fine hot or cold and purrs like a kitten when the boat is up on the plane. My agent said it was fine when it went in for a service last.

    Regards John
     

  3. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    If you haven't set your carbs in the water, under a load, then you need to do that. It might help with the excelleration and elliminate your shudder when coming off idle.

    Just because the book give a starting position to the low speed needle, that doesn't mean you shouldn't try to adjust it even more to get the best low speed performance out of it.

    You'll need some help with this though. At idle, in gear, not tide up to the dock, adjust one at a time until you get the best performance.

    Turn the needle in, or out 1/8 of a turn at a time, wait a few seconds to see what it does, then continue, Get one as best you can, then move on to the next one.

    John, it works on Yamaha's also. Running on a hose is no way to get the carbs adjusted.
     
  4. jbarnes17

    jbarnes17 New Member

    Messages:
    536
    State:
    Commerce, Oklahoma
    I had a 63' 100 hp Merc. that had to have the carbs adjusted while under load just like Bob said. Its easy to do, it just requires two people.
     
  5. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC

    Thanks for the back up!:lol: