Voltage drop on dash gauge and alarms

I'm looking for suggestions about an electrical problem on my 86 Ski Nautique with 351 and electronic ignition.

Scenario: The volt meter gauge is registering about 1 volt less than what is being output by the alternator (when running) or the battery without the engine running. I've tested the battery (only one year old and it starts the boat no porblem) and the alternator (about 13.7V at the terminal). I've also tested the meter and it is reading correctly about 1 volt less than already mentioned. Additionally, when I turn on the blower or lights, the voltage light comes on and the alarm sounds showing 11.7 volts (agrees with waht is on the dash volt meter and my portable volt meter), but the alternator and battery still show 12.7-13.2 volts. I've also checked the power to the switches and it's the same as the battery voltage. The power from the ignition switch seems to be about .5-.8 volts less than the battery or alternator. Additionally the boat starts great and runs great other than this. If it didn't alarm, I would have guessed that it was the voltage gauge. I think it might be the ignition switch. This is a new problem within the last two weeks.

Questions:

1. Is there a voltage drop across an ignition switch and if so how much?

2. Is there something else I should be looking at?

3. Anyone else had this problem and what did they do?

More likely than not, it is probably a grounding problem partly due to the guages being wired in series as Siveck mentioned. Run seperate ground wires to each gauge from the main ground wire or clean up and tighten all the ground points.

My 84 had a number of similar problems with the wiring. I discussed it with the EE's at work, and the following steps have cured what ailed me:

1.) Solder up every crimped or slip together connection. Do it right over the corrosion. That was their advice and i'ts worked great for 5 years now.

2.) Disconnect the multi conductor plugs and coat the pins with tune up grease.

The voltage drop from my battery to my gauges is now 0.3V, and from my dash to the + terminal of my coil 0.2V. I haven't added any new or bigger wires, I just fixed up the old ones with good results.

Well I figure it out. I replaced the ignition switch and the volt reading went from 11.9 to 12.2V. I also cleaned the ground contact on the engine leading to the dash, which added .1V (12.3V). I replaced the Red + lead wire from the ignition circuit breaker to the switch and added .1V (12.4). I tested the battery Voltage (12.57) and hooked up temporary wires to the dash and was able to get .1 more volt. I decided to add an additional ground wire between the - bus bar and the end of the ground wires by the volt meter. I placed a Y connection so the volt meter reads from the bus bar and the instruments get an additional ground.

I removed the temporary battery wires. I get a voltage of 12.5 at the volt meter and across all gauges without running the engine. I get 13.5V while running, 12.8 volts running with the blower and all accessories turned on. (total time working 1.5 hours)

It was definitly the ground wires. Problem fixed (and my dash light are 50% brighter too).

Thanks for everyone's input including Vince at SKIDIM.

Isnt it amazing on how inadequate the wiring is in boats?!