[jclark003]

The 3208 is a very good engine. 435 is the high end of the HP range for that engine however. They will be less tolerant of abuse and if run hard and or run over loaded, engine life will be significantly reduced. Make sure it is propped to exceed rated rpm by 2-3% with the boat loaded up. Follow maintenance schedule especially as it relates to cooling system and keep it under 80% load while cruising. Go to boatdiesel.com and you will find loads of great knowledge on how to run and maintain them.

In terms of volt reading, mechanical gauges can be notoriously inaccurate. Start by connecting a digital volt meter to the battery bank, turn off battery charger and run up the engines. You should see 12+ volts before starting engine and closer to 14 volts when over 1000 RPM. If no change then time to look at charging system. At 10 volts I doubt you would even be able to start engines. Check both banks. Typical to have one engine charging start bank and the other charging house bank.