79' Merc 140; having problems with response time. Just did plugs, and coil(was cracked).

After changing coil, startup was good, still sluggish until revs get higher then all systems go. Still after stopping, can't get full throttle response right away. Local dealer says switchbox needs replacing; where else should I check first? Fuel filter screen I also checked,good.

Trouble shooting is the way to go -------------Lots of posts with ----" replaced switch box and motor still runs the same "------------put a timing light on each cylider and see if you have a steady flash on each as motor revs up.-------------Common for them to idle really nice and stumble on acceleration and the fix is to open up the low speed needle mixture screw an 1/8 turn on each.----Then try again untill stumble is eliminated.

Hold it! Do the carbs on your motor have bolts to attach them that go all the way through the carbs (WM-11 to 13s)? If so, I have the solution to your problem.

Jeff

Jeff , the man states that it is a 79 ----140-------------Just the same as they have always been -------An inline 6 cylinder !!

Okay. I've had a lot of bogging problems with those carb and--just recently--I found a way to cure it completely. It requres removing the carbs from the motor, but I can assure you it will be worth it!

The below photo shows a line of vertical holes in the throttle butterfly. While holding the butterfly closed, drill all three holes out to 1/8 inch. Be sure to blow away any chips before reassembly.

Jeff

PS: Again, this modification applies only to that model carb! If yours doesn't look like the one in the photo, let me know.