Re: 71'Mercury 135 L6--NO SPARK?!*%!?
Db, 9 out of 10 times, it's the ignition/switchbox that goes bad. As chris stated, it is located on the inner cowling frame right in front of the carbs. There is a method to test it. First, do the test that chris spoke of, then rotate the flywheel until the number 1 piston is near Top Dead Center (TDC) then locate the 3 wires on the box where the distributor wires hook up...disconnect the 3 distrib wires from the switchbox (there's a black, white and brown wire from the dist.) with the distrib wires disconnected from the switchbox, put a jumper wire between the brown and white terminals on the switchbox, now make a wire about 8" long, hook one end of it to the black terminal on the switchbox...turn the key to the on position...now take that wire that you hooked to the black terminal and "strike" that loose end to the motor framing (ground)...it should make a spark when grounded, if you get no spark, it is the switchbox, if you get spark and can here the coil clicking when you strike that black terminal wire to ground, then it is the coil. Most likely it is the switchbox.
