I have a 31' Chris Craft Commander with twin Detroit 8.2T's. It is 12V. The problem that I am encountering is that I cannot start either engine from the start buttons. When I try to, I turn the key switch and hear the fuel solenoid click on and hear the oil pressure buzzer as I normally do . When I press the start button all I hear is the starter solenoids clicking and the engine does not crank. At first I thought it may have been that the batteries were to low to activate the starter. I charged them up and still nothing. I load tested them and they checked out fine. With a voltage meter I tested at different points. At the solenoid, key switch, and the start button I measured 12.7V. When the start button is pressed the voltage on the button drops to 8.4V. I can however jump the solenoid and crank the engines over and run them. I tried to run a new solenoid wire from the start button back to the solenoid and jumping over the button and key switch all together. None of which worked. I also disconnected the wiring harness in the engine compartment. With a key starter switch with alligator clips on the 2 wires, on the engine side of the harness, I made a connection between the power and solenoid wires. I turned the key and the same thing happened. All I heard was the solenoid click. I checked the wires for breaks or damage and found nothing visually wrong with them. I changed all connectors and cleaned up all the terminals. I bought 2 new solenoids and rebuilt the starters. I also isolated the starting system and made sure there was nothing else stealing power of it.
I'm at a loss here. What else can you recommend doing?

I have tried everything to isolate the start system circuits. I have removed anything that was on the line, checked all the grounds, all the connections, the terminals, all the devises, switches, buttons, and all the wires to and from each of them. I'm out of options besides sinking the damn thing and collecting the insurance $$$.....Can you tell that I have lost it!
I'm scratching my head. If there is anyone out there who has encountered this problem or may have an idea of something that we have overlooked PLEASE let me know.

I measured the voltage along the circuit. I got 12.7-12.5 volts from the battery to Perko switches, from the switches to the solenoid, from the solenoid to the in dash breaker, from that breaker to the key switch, from the key switch to the start button. When the start button is pressed the voltage drops to 8.4V on the delivery side while when it is not activated I measure 12.6V on the feed side. I thought that maybe the button was bad so I replaced it and got the same results.
I also ran a new wire from the solenoid post with the B+ to carry the power to the dash to cancel out the feed wire being bad. I also ran a new wire back to the solenoid from the start button to cancel out a bad starter wire. I jumped over the Perko switches with jumper cables to cancel them out. There is not much left to check. If anyone has any ideas or has encountered this please let me know.

 

When you rebuilt the starters did you check them out of the car ?

Have you tried bypassing all the wiring and just connecting the solenoid to the battery to crank it ?

 

Yes when the starters were out of the boat they were checked.

 

How have you been jumping the solenoid? From the battery post to the starter feed post or to the solenoid engage post?