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For Best Performance - Check Your Throttle Body Linkage Adjustment

Thread in 'Motors & Props' started by Reelslow, Nov 3, 2017.

  1. Reelslow

    Reelslow Member

    Likes Received:
    Oct 3, 2017
    Phoenix, Az
    This will likely affect MANY of us since I found the issue on my boat and another on the showroom floor. Basically, the TB was not adjusted worth a crap. At 100% throttle at the helm, the butterfly was open maybe 85-90%. This was on my 115 4S. Also, good lord they used HUGE hex bolts on the butterfly. With a throttle body this small, there will be a measurable gain from proper adjustment and going to a nice slim stainless button head with washer (don't forget the loctite!) To note, the bolts on the 75, 90 and 115 are M4 x 6mm long if you feel like tinkering. With an engine this large (just under 2.1L) and a TB this small, air velocity will be high. So details like this are IMPORTANT if you want all your motor has to give.

    Some before and after adjustment photos.

    Before the linkage adjustment (adjust vertical rod that goes to the TB)

    Butterfly position at WOT before adjustment:

    Properly adjusted:

    How the butterfly should look at WOT:

    Be careful not to over-adjust the linkage or it will not let the butterfly properly close when at idle resulting in a high idle condition. I recommend having a buddy, kid or wife help out and control the throttle while you adjust. Adjust in 1/2 turn increments just until the stop touches the TB at 100% and go no further.

    If your engine was like mine, proper adjustment and getting rid of those huge bolts will result in a nice increase in top end.
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