[BruceK]

Appreciate your help.
Our esteemed late member FF (Fast Fred) could reel off charging profiles for most batt types, alas no longer.
After "online shopping", I was at the boat today measuring the existing batts. Another Optima Oddessy is about all that fits the bowthruster location, about $300 AUD.
The Genset 150Ah batt(? 6D in US parlance), was alarmingly hot. Constant unsuccessful charging, electrolyte diminished, > high heat, is bad. A neighbour`s SLA exploded last week. I disconnected it pending replacement, charger and 8D can relax now.
The aim is to go all AGM so I`ll replace these 2 with AGMs. The 8Ds are at least 3 years old, test well, but in time will give way to AGM. I`ll try checking individual battery profiles to see how close Flooded/SLA/AGM are. Failing that, the most important batts are the 8Ds. I wonder how charging the 2 peripheral batteries via an 8D SLA affects things, the peripherals are not talking direct to the charger. Not sure but I think combiners are just voltage actuated.
We are making headway. Unfortunately both electricians I wanted to try are away interstate for several months. Marine service people are thin on the ground here.