Westerbeke Alternator not charging/no tach

[Storyteller 20]

I have a 2005 Westerbeke 82b four. The original owner got the 190a alternator with a balmar ars-4 external regulator. The tach has been working intermittently since I bought the boat about a year ago. I figured it was a loose wire etc. About a month ago it stopped entirely and I also realized it is not charging. I was getting no voltage from the pegs of the alternator and only about .4 acv from the tach wire at both the end and the connection on the alt. So i figured alternator not voltage regulator.
I've replaced the alternator with an off brand 100 amp, and changed the belts while I was at it, but I'm still only getting .5-.7acv for the tach when throttled up and .8-.9 dcv on the alt pegs. Tried it with the wires attached and without. My next thought is the ext reg, but those are at least $300 and I'd rather not play the replace all the parts in the line game. Also the tach wire goes straight from the alt to the gauge, so not sure how it would be effected by the reg. There is also a battery isolator between the alternator and the regulator. I am new to high amp alternators so any trouble shooting advice etc would be appreciated.
Thank you

[Wotname]

Welcome abord CF, Storyteller 20.

It sounds like the alternator is not getting any field voltage/current from the external regulator. However before replacing the regulator, try checking the field wiring (and terminals) between the regulator and the alternator.

Measure the volts on the field terminal of the alternator.

Also measure the volts on the sense wire of the regulator (it should be the same as the battery terminal voltage).