My new to me '81 Formula 255 Liberator w/twin 260 Mercs "went dead" a week ago on its first venture on the water. After running for about 30 minutes with the battery selector on "both", one engine stalled and then 15 seconds later the other stalled (this happened at idle). While running on the water we noticed a burning smell -- like plastic or something, not burning oil. This may or may not be related to the electrical issue. The batteries didn't have enough juice to start either one once they stalled. I've since bought new batteries and using one battery, I fired up each engine separately on the trailer. When the battery was sitting new it read 12.76V -- when either engine was running it read 12.45V. They both started and ran well, but it's apparent that neither alternator is putting out voltage, or if they are, something else is stealing it away. Both ground cables are secure to the blocks, but I haven't had a chance to check the wires from the battery to the starter. I assume if they were loose there would be difficulty starting. Doesn't the alternator wire run to the starter to charge the battery? I also checked the B+ cables for each engine where they connected to the battery switch to insure the switch wasn't the problem, and I got the same readings there. So it appears that neither alternator is functioning -- or at least any voltage being generated there is not making it to the B+ battery cables on either engine. Something else interesting happened last week when I wiggled the ground cable for the port battery while the star battery was connected. The sink water pump turned on! I have not been able to get that pump to run (it ran when I picked up the boat), and also some of the cuddy lights do not work. I have no idea if any of this is related to the alternator issue, but I'm guessing that it might be. Any suggestions would be appreciated.