I have owned a 2003 Catalina 310, equipped with the OEM Universal M25XPB diesel engine which is a converted Kubota farm tractor unit. That engine has always been a royal P.I.A. since I have owned the boat. This season, I have noticed that the voltmeter reading doesn't go above 12 volts, even with the engine at full throttle, suggesting a faulty alternator. The engine starts up and runs fine. Due to long covid, I am only daysailing this season and just need the engine to get me in and out of the harbor. Is it safe to use it this way, as long as I keep the 2 group 4d batteries charged up.