Re: 1979 20hp thunderbolt. HELP
Not sure if your neutral max throttle rpm limiter piece is messed up or the throttle linkage has skipped a tooth. And there are stop screws to set the idle and max throttle opening with a nut to lock the setting
Suggest you get a Mercury factory service manual or Seloc for your year and follow the timing syn section. These manuals also have pictures of what it supposed to look like. Also might post a picture of your throttle linkage here and maybe someone can help.
Good luck and great motors!
