[Rockfish9]

start with the ground at the starter to the block... check the crimp... if you see any sign of green replace it..also check the grounds that attach to the block at the starter solenoid... they have a propensity to loosen and corrode. Check the in line fuse holder at the starter solenoid... they provide power to the key switch and trim solonoids... if all that looks good and tests fine...it most likely is the key switch... they are a prime culprit for this type of grief....if I were a betting man..I'd look real close at the solenoid grounds and the wires( in line fuse) that provide power to the key and trim.. seeing the 2 are related and merc. branches the power for the trim and key from the solenoid connections because the trim should be live even with the key off.