1988 40 yamaha

Discussion in 'Bubba's Outboards' started by catfever, Mar 10, 2007.

  1. catfever

    catfever Member

    Messages:
    91
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    conway,s.c.
    Got a 1988 40 yamaha, runs good thru the rpms, but it idles kind of rough, carbs have new kits and cleaned well, checked for air leaks, i did link and sync as a friend told me (good marine tech. before got sick), but i dont know if i got it right, could it be timing or ign. problem, i have owned it 12 yrs. and never checked timing, its harder to start cold than it used to be, any ideas, thanks
     
  2. Bobpaul

    Bobpaul New Member

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    Have you done a compression check?

    Who did the carbs and when?

    Was the fuel system flushed and the tank cleaned?
     

  3. catfever

    catfever Member

    Messages:
    91
    State:
    conway,s.c.
    Compression was 126/132/130, I did the carbs myself last fall, soaked them chem dip for 1 1/2 days , all passages clear, low speed, etc., system flushed with new tank and line, the problem was there before all this, i trust my carb work (not trying to brag here, i build auto race carbs myself), i use stabil in fuel, any ideas ?, thanks
     
  4. Bobpaul

    Bobpaul New Member

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    It sounds like you did everything right. I'll have to check a few things on Monday and get back with you.

    Did you adjust the carbs at idle, in the water, and in gear?
     
  5. catfever

    catfever Member

    Messages:
    91
    State:
    conway,s.c.
    Hi Bob, I set idle mixture in water in gear, got it the best i could get it, ended up being about 1 1/4 turns out, before i took it to the water i checked timing, idle timing was at -8, i brought it up to -5, that help alot with the idle, i read somewhere timing on this engine was -5 at idle, is that right ?, wot timing is at +24, i didnt move it until i can find out what its supposed to be, you can give it throttle it runs good on the water but theres one spot in the range of throttle on takeoff it seems to skip or shake, i have had the roller on the throttle loose before and not sure if its adjusted right, any ideas, thanks
     
  6. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Hell, it's Saturday and I've not been to the shop all week to get the proper set up info for you. Sorry about that, but it's been a busy week for me.

    At idle, the throttle plates should be closed tight with the linkage disconnected. Back off the idle screw and connect the linkage. Adjust the idle screw to get a good idle, about 700 rpm's when in gear. At WOT you should see the pin on the outside of the shaft that holds the throttle plate in the carb, should be in a verticl position, indicating the throttle plate is in a wide open position.

    The timing you mentioned sounds right, but I need to check specs to be sure. I'll try to get the info today.