Re: 1956 15hp johnson ?'s
Top knob is idle speed adjust, called the low-speed jet. Bottom is the high-speed jet. Turn both clockwise gently until they stop, don't torque them down. Back the top jet out counterclockwise 1 and 1/2 half turns. Back the high-speed jet out 3/8 to 3/4 turn. Run the motor in a barrel or on the boat, with leg submerged of course. Get it runnning and throttle up slowly, adjust the high-speed knob a little, generally clockwise (lean), until it runs best at speed then turn it counterclockwise a little (rich). Now tighten the nut around the needle, behind the face plate, until it takes some effort to turn the needle. It should be tight enough that the adjustment you made won't come undone with vibrations from the motor running. Adjust the low-speed jet the same way, throttle down to an idle and adjust to find its sweet spot. Tighten that nut, too. If you do this with the motor in a barrel/tub, you'll have to readjust/tweak both settings a little once on the lake. After that is done, note the settings for future reference. I like to loosen the knob screws after I find each setting, reset the top knob so it's pointing to 6 oclock and lock it in that position. I set the bottom knob at 12 oclock. Be sure not to turn the jets when you're tightening down the knob screws, you have to hold the jet shaft with a pliers, etc.
If any body here has a 15hp or 10hp they would like to sell me pm me!
