Voltage warning light

While running with all accessories on, the voltage light comes on. I have checked the alternator and it is putting out 14.1 dc volts. I have also checked the battery which is less that a year old and it is putting out over 13. The volt meter on the dash seems to run about 13-14 without anything else running. When all is on, it goes down to around 10-11. Any ideas to the cause? This is on a 1990 Sport Nautique.

Try the search feature and you should find several threads on the early 90 Correct Craft wiring issues. It is known that those boats did not have a large enough power supply wire from the relay up to the dash but an equally big problem is the lack of adequate grounding on those boats. The installer who did my stereo install taught me a little about 12 volt electrical. He stated that most of the time 12 volt electrical problems are not a lack of enough power but poor grounding.

Here is some info from one of my prior threads...

"I have been restoring and fixing all of the gremlins in my 92 SNCB for the last few months. I am now working on the electrical system. My boat sounds like the other early 90's models with poor grounding in the dash and gauges along with what appears to be inadequate power supply wire from the battery/solenoid up to the ignition switch on the dash. I have just upgrade to the GT40 100 amp alternator and added a second Odyssey battery for the stereo system and that part is working great...it is just the gauges reading inaccurate and/or not supplying enough power needed such as dim dash lights/nav lights/perfect pass flipping on and off with numerous accessories turned on at once."

I added two 1,500 AMP HD batteries, new cables, and the 100 amp alternator which helped but did not totally cure the problem. I then added an individual ground block under the dash and ran a size 0 gauge ground wire to the second battery. I then opened up the dash and found numerous accessories and gauges all T spliced onto very small grounds. I then ran individual grounds from every accessory and gauge up under the dash to this ground block along with Dielectric grease on the terminals and ground blocks. Bingo...no more accessories turning off such as Perfect pass and the temp gauge would not jump when I turned on the Navigation lights.

Second...I ran a size 8 gauge heavy duty power supply wire from the rear relay all the way up to the ignition switch. You then have to run an 8 gauge wire out of the ignition wire over to the key switch because it is in the 12V supply line. It only has 16 gauge wire from the ignition switch on the dash over to it so it is a bottleneck for 12V supply. All of the main wires feeding from the ignition switch, keyed switch, and back I upgrade to 8 gauge. I can now turn on my Nav lights, (2) cigarette lighter accessories, blower, bilge pump, depth finder, floor lights, Aqua clear pump (yes it still works), stereo (1,000 watts), and perfect pass and still hold 13.0 volts and nothing fades or get's weak. I also changed out the key switch as DIM stated they can go bad and cause power supply issues. I would at least try the ground issues first as that helped me alot. Look under the dash and if there are alot of small ground wires sharing one circuit try to separate them and find or create a new grounding block somewhere. Some here ground staight to the block. Also...on the front of the port side of the engine there are a couple of heavy wires grounded on the block. Clean them good and remove any rust, apply dielectric grease and tighten them up as that could also be a problem area. I would also change out the ignition switch on the dash if yours is original. Mine only lasts about six or seven years and it gets weaks and pops. Hope that helps!

Thanks!