Charging mystery finally solved
We have owned our boat since Aug of 2013 and enjoyed many day trips with only one night on the hook. The po told me the charging system on our trawler was designed to recharge the entire double house bank (parallel setup) plus the 8D starting battery while underway without assistance from shore power. With our limited use away from shore power, I never really saw that this system performed as advertised. During this springs system checks we noticed arcing from a loose alternator connector and then the tach quit. This prompted a visit from the marina electrical guru who found the system was not working at all and with our habits being short trips out (a day or so) followed by shore power charging, we were actually camoflaging the fact that the system was not working. It may have been faulty for awhile. The electrician pointed out that the only power the diesel needed all day was the original start in the morning which was no problem because the 8D had been shore power charged prior.
As recommended we had the alternator rebuilt and a new voltage regulator installed and for the first time found it charging each bank (2 banks) at 75 amps while underway! The result is that everything seems to work better now - even the gauges seem to work better and we arrive back home with all batteries fully charged just as the original owner suggested. I think they said it is a three or four?stage alternator, twin belts, 200 amp rating that only now seems to be pulling it's weight. The po told of many long cruises where he only had to run the engine for 3/4 of an hour each morning to top up the system after the night before. Our boat has no generator, but dual 12/110volt systems throughout.
This is likely not new to the more experienced members, but it may get some owners thinking , especially diesel owners who just do day trips as we were. Looks like we finally have the boat with all systems operating as intended. Now we just need a destination!