Re: 25 horse Johnson backfires and stalls.
sounds like a link ans synch would be in order, from your discription I assume the horizonal piece is cam shaped and the nylon roller rolls along it and causes the carb to open. Not sure what exact link and synch proceedure is for your particular outboard, but a link and synch is simple once you know the proceedure and can't hurt.
that said a stumbling backfiring idle is often an indication of a lean low speed needle setting, suggest you adjust the low speed mixture knob (which i assume is on the front of your engine cover) to a richer setting.... generally you set it to best idling position on warm engine, then pull it out til it pops off, then set in center of travel, when you start cold you set to rich, then move to center when warm. (these directions are based off of 1983 15hp, and I am assuming simular configuration.
Will see if I can find link and synch proceedure in my manuals, also suggest you get factory manual for your engine... ebay has some pretty good deals.... have NOT been impressed with seloc and clymer manuals.
sean
