A failed ignition return switch on our boat caused our starter to remain engaged after the engine
started the very first time we started the engine
after having taken possession of our "new" old boat. That turned our starter into a generator
which quickly failed the entire electrical system
including the shut-off solenoid. Before we finally got the engine shut down manually, the entire starting battery
was melted and all the insulation
on all of the cables
were burned through. The result was a $1,600+ repair!
We now, routinely, lubricate the ignition switch to ensure it's correct function and test it frequently--with the engine battery
switch truned off--to make sure all is well.