OK, I am in the fortunate position of having two MDCs
so I tried voltage from the each of the three 5 pin connectors that go to the gauge and am getting 17.5mV when it should be reading 7V. From the blue and black, I'm getting 0V when it should be reading 12V. Using the second MDC, the red/black read 17.7mv and blue/black 0V, so the MDCs appear to be about the same, so I suspected the harness. I found one glass 5A fuse on a black line and even though it looked OK, did a continuity on the ends and confirmed. I didn't realize there were two more fuses in the yellow casings until I reviewed Technical Service Bulletin #38. They are in the picture to the right of the yellow wire wrap I put in. I checked these and one fell apart. I tried Radio Shack and Autozone and nobody sells 3amp Buss type fuses that are the same size. So at Advance Auto, I bought two Heavy Duty ATC Blade Type Fuseholders that use the push in blade fuses, Catalog No. BP/HHG . Soldered and taped and dropped in 3A blade fuses and now....tada I have gauges! I have never seen the gages move in this boat I've had for two years until now. Motor cranks now but the engine doesn't catch. It did the first time I cranked it out of storage last week, but nothing but starter motor now. The tank was bone dry so I put 10 gallons in today, but still doesn't catch. even with the primer button. I'll change the plugs tomorrow. I'm not worried since THE GAUGES WORK!
I feel a lot better now that I'll be in the water soon.
