Re: 60hp johnson
Don't assume it is the amplifier. Do some tests.
Test for voltage at the amplifier input with key on. If ok, go to next step.
Remove the coil and then unscrew the spark lead from the distributor cap by turning the whole coil and wire assembly. Then re-mount the coil and rig up a 1/4" spark gap off the end of the wire.
Now, disconnect the wire running between the amp and timer base under the flywheel. Turn key on. Brush the amplifier end of the timer wire across a bare metal grounded part. There should be sparks off the end of the spark wire.
If you get sparks, the amplifier and coil are good. Pull the flywheel and see what is wrong in there. But if no sparks, you have a bad amplifier or bad coil. Take your pick.