Yes, alternator. The boat is a 1984 Farr with a Lees marine BMC Captain and 55A Ingram alternator so the regulator is probably 90's vintage. There are no visible model or serial numbers. I'll remove it over the weekend and see if there is anything on the back. Connections are via a moulded 8 terminal connector (spade type). I can trace the wiring and the obvious connections are there but what is confusing is for example there are 2 connections green and purple running back to the battery negative post..
The connection tracing began when i had no charge on running the engine last weekend,