On a recent cruise the engine would not start ....there did not appear to be any power to the starting button although the key was on.
The easy stuff (if you have stock Ericson wiring)
1. With the battery switch and key switch on, is there any power at the panel (gauge lighting? volt/ammeter? low oil pr light?)? If no, check the 20A inline fuse in one of the large (10 ga) red wires feeding or coming from the key switch.
2. If panel has power but starter doesn't crank, check the 10A inline fuse in the yellow-red wire feeding the starter solenoid (the fuse is located near the engine, not the panel).
3. If the fuse is good, go back to the start switch. Unscrew either lead on the back and touch it briefly to the other lead (I.e. bypass the start switch). If it cranks (be prepared for that) it's your start switch. If not, repeat this last step while holding the glow plug button (some setups power the start switch only when the glow plug switch is activated).
4. If still nothing, try touching the starter wire to the glow plug switch's feeder wire (I.e., bypass both the start and glow plug switches). If none of that works, you need deeper elect troublehooting.
Only good news then is that the starter circuit is grounded only by the starter's contact with the engine, so there are no other grounds to troubleshoot, only "hot" wires.