flat spot???

M

maineiac5586

Chief Petty Officer
Joined
Feb 14, 2009
Messages
645
i have a 76 merc 500, have a bog when acclerating from dead stop also from any throttle setting under acceleration. idle is good, starting is excellent. i tried adjusting mixture screws on front of carbs , doesn't seem to make any difference. in fact i could hardly tell any difference from 1-1/2 turns out from lightly seated all the way to 3-4 turns out, motor still seemed to run same. idle speed did change a little though. spark is good and engine pulls top end rpm no problem. any ideas??????
 
C

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: flat spot???

Generally, any hesitation or bog on acceleration is a sign of a slightly lean idle mixture.

Readjusting the idle mixture screws out about an 1/8 turn from their position set at best idle speed while IN gear on the water.

Since you've already tried this and don't seem to get a noticeable change in performance it may be a safe bet that it is time to clean the carbs.
 
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