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Electrical/Starting Problem with MCM 200 / 5.0L V8 Alpha One

C

cow

New member
Hi, I got a '94 Ebbtide SE from a family member that had sat idle a couple of years. Short story, my buddy and I got the motor running after replacing the ignition coil, replacing the battery, new belts, and changing oil/gas/drive fluid, plus general cleanup. It ran well, everything was working, then it sat for about three weeks while we had lots of rain. Uncover it, go to start it, nothing, not even a click. Electrical works though - radio, gauges, blower and bilge work. The shifter is in Neutral.

After some fiddling around, and charging the battery (mostly at 30amps, but sometimes at the 120amp setting for a few minutes), I got it to a single click when turning the ignition key. We suspected the neutral safety switch, not letting it truly get into neutral. What I tried was jumping the top terminals on the solenoid - got one crank but no start, but would get spark. I tested connectivity from the positive on the safety switch to the positive terminal on the solenoid and it was about 7k ohms. I figured, that must be it. So, I cut the wires to the safety switch and jumped them together. No change. To experiment, I disconnected them and measured resistance from the white/green wire that was going to the switch, and got something like 80k resistance to the solenoid. So, I guess there's a problem somewhere in that wire lead. What's more, though, is in testing these things I apparently now have a short in the circuit. There's full continuity between the heavy wires going to the solenoid (Yellow/red, Red/purple) - 0 ohms between these wires (I disconnected them from the solenoid to make sure it's not the solenoid). In addition, voltage is getting sucked from the battery somewhere - it's not flowing through the starter motor like it was. When I discovered the short, I disconnected the battery. I'm also guessing the circuit breaker is tripped or failed from the short or the jumping, but I can't physically push in the reset button ( I can't tell if it's jammed or just not tripped, or just not working).

Some other notes - despite covering the boat up, there's still lots of moisture that builds up in the boat and the engine. There's some corrosion on some of the terminals around the engine. I've sprayed them all with contact cleaner and tried cleaning with a copper brush. That's my adventure. What advice ya'll got?
 
Using a voltmeter trace the circuits
Start Circuit Merc.jpg

Check for 12V on both sides of the breaker

It might be the key switch or fuse behind the helm.
See that there is 12V on Red/Pur on key switch.
Turn key to run and verify 12V on purple wire
Turn key to start and verify 12V on Ye//Red

With key in run verify 12V at + side of coil
 
without they key in, i’m getting 5V across the starter, across the circuit breaker, as well as at the key ignition switch. Same at the Red/Purple wire connection at the solenoid. (There’s also still an open line between connections at the solenoid). If I turn the key to run, it’s closer 8V but fluctuates down to 5.

the battery shows 12.5 V.
 
without they key in, i’m getting 5V across the starter,
Click to expand...
Measuring 12.5V at the Bat and only 5V at the starter, you have either a bad Bat cables or your not getting a good ground. If the Negative Bat cable is corroded and not making a good connection to the block, all readings will be bad.

Remove both Bat cables from Bat, Starter and Block. Try to look under the insulation jacket of the cables to see if you see corrosion (might be green). Clean them up real good so they are shinny metal and re-install
 
Ok, I removed, inspected, cleaned, and reinstalled the ground connections to the starter and battery, and the ground connector going from the starter to the helm. still no change in voltage.

I am still reading continuity between ground and the yellow/red wire
 
No offense, but I'm thinking there might be a problem with how your measuring voltage, or there is something wrong with your meter.

Your post list reading 12.5V at the Bat terminals (Black on Neg and Red on Pos), if this is correct than your Bat shows it's 90% charged, full charge is 12.7V. 90% is enough but just noting levels.

When measuring voltage at the starter, the Red probe goes on the starter post with Bat cable, the Black probe goes to a good ground like one of the starter bolts, that is if there is no paint on it. Are you still showing 5V when measuring these points? If you are, go back to the Bat and turn key ON and does it still show 12.5V?

I would not pay any attention to continuity between ground and Yel/Red until you can measure correct voltages on starter post and both sides of the circuit breaker. The next reading would be full voltage on the Red/Pur wire at the Key
 
Great news, I got it cranking. I removed, cleaned, and reinstalled my wires for the battery, starter, solenoid, breaker, and ignition, and double checked that they were all going in the right places. Measured 12.8V across various connections, got the electronics working again (with brighter indicator lights than before too!). It's not completely starting, but that's an issue for tomorrow. Thank you SO much for your help!
 
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