I have a 1996 Glastron GL185SF with a 4.3L Mercruiser I/O Alpha LX....starter won't disengage after engine starts (acts as if ignition key is in constant "START" position) ...I've replace ignition switch, and the (previously burned up) starter, and installed a new 12V battery with 550 CCA, 750 MCA...what's my next troubleshooting method?...where is the continuous load to the starter coming from?...I have a suspicion it may involve the assist "slave" solenoid....can someone explain the "slave soleniod"? - if so, how to test and where is it located?...lastly, does this slave go bad often? - if so - what's the cause?....thanks.