Twin 1996- 454s EFI Marine Power engines with a ECM . Toggle switch instead of standard key , same function, Mom on ( on ) - On - Off . Swapped switches, same result , not the switch. Wondering what is being killed and will try and back trace it from there . Any suggestions besides that ? I shut it down at the main control panel in the cabin , which has separate off - on ( no start ) switches for each engine as well. I have upper - lower controls along with main control panel and wiring goes into looms never to be seen again .