318 wont stay running

Hello, I have a 1981 silverton 31c with twin 318's. I'm refitting the entire boat, and I'm trying to get the motors running again(they haven't run since 2009) The Starbord motor starts and runs fine, but when I just tried to start the port motor, it fires, but when I let go of the ignition key, it dies. I'm pretty handy, but I'm not an expert in engine electrical. My friend said to check the coil wires. On the motor that runs, with the key on, the positive coil terminal has about 5V with respect to ground. the motor that won't stay running has 0 volts on the positive terminal (with the key on). I tried swapping starter solenoids with the one from the running motor, which is where the positive coil wire goes. That did not help. Is anyone familiar enough with this to give a suggestion on what component or connection to check or a test I can do. I know this is a little vague, but any suggestion would give me a place to start.

Thanks

Swap ballast resistors and see what happens. or provide 12V via a jumper to the + of the coil to see if it stays running.

will

Since the engines haven't been run in 4 years check all the electrical connections for corrosion, also check the ignition switch itself. When this happened to me it was the breaker to the ignition switch, a simple reset, if you have one.

Thanks for the quick responses. I'm not sure if this will matter, but the rebuilt vessel wont have a flybridge, and I did have dual stations. so the connectors (plugs) that went to the upper station are not connected to anything. Is there a way to check the ballast resistor? I'll have to locate it. As far as the ignition switch breaker is concerned, are you talking about one of the 2 pushbutton breakers on the top of the engine? Also, if the breaker has tripped, would the starter still work (mine does, and the engine does fire until I let go of the key). I did check those breakers, by just checking continuity across the contacts (not sure if that's a valid test, but it would seem so).

Thanks

My boat has 2 breakers on the engine also, it was not one of these it was the third one located on the dash board. Yes, the starter still worked. The ballast resistor should be a simple continuity check.

Check the connector on that ballast resistor. The one Chrysler used was crap. Stranded me in the middle of the Bush River once.

Jeff

Thanks for the information. I'll definitely check the resistor.

Silverton used one - or sometimes two - electrical connectors between the engines and the wiring to the helms. They are easy to find, running right over the transmission. Both are prone to failure. Pry the one closest to the engine apart and carefully examine the pins. You may find one or more heavily corroded or even missing. This is a common problem with Silvertons of that period. Power from the ignition switch to the ballast resistor (and then on to the coil) goes through both of these connectors.

Old dodge guy here; ballast resistor would be the first thing to check.
Buy a spare or two, they are prone to failure without warning.
On the rare occasion, the ECM or spark box give up, should be relatively close to the ballast resistor with a multi-wire connector held by one screw.
ballast resistor is roughly rectangular in shape, with a hump in center with an oval hole, two male spade connectors or a single spade connector at each end, usually white or light gray.
re-reading your post, you nailed the ballast resistor with your troubleshooting. 0V at coil, switch on.