I just put new batteries in the boat. They read around 12.7 When I turn on the engine and take readings, they are around 14.5 Is this increase significant?
12.7VDC is aprox a fully charged battery. The 14.5VDC is the alternator charging the battery. Don't have time to educate you on battery electro-chemistry in this post but you could read "Nigel Calder" on boat systems or read one of the boat electrical books by "Spa Creek Press".