Sean, where are you checking your voltage? At the batteries? At what engine speed? You might check with your engine's mfg. and see if you might need a new voltage regulator. Are you using a separate meter at the batteries to check your voltage output? Have you installed a battery separator to charge one battery at a time? Just know that one battery can discharge the other if connected together. One can steal the charge from the other, depending on the internal condition of each battery also. Nice to find out now, rather that half way to anywhere. Might be a good idea to check the water level too, unless they are sealed and you cannot check them. You might have a poor connection somewhere in the system also. Hope this is a help. Don't have a boat yet, lots of experience in trucks though. As stated else where on the net, know this advice is worth what was paid for it. Ken Dado PS. sometime ago I wrote you about a NorSea 27 in Vallejo, what happened? Ken **************Wondering what's for Dinner Tonight? Get new twists on family favorites at AOL Food. (http://food.aol.com/dinner-tonight?NCID=aolfod00030000000001)