Alternator/Regulator Mods
Jim Norman, Jos Sonneville
8/1/2004
Hull #:     33

We’ve had a lot of “traffic” on our Sailnet email discussion list on this topic. Modification of your engine’s alternator, to provide connection for a “smart” external regulator, can make the full alternator output available for your battery charging; otherwise, the typical alternator’s regulator will provide only about 1/2 of the available charging current.

The particular description here is applicable to the earlier C380’s that have the Westerbeke 42B engine, which includes a 72-amp alternator. The same concept will work for the Yanmar-equipped boats, although it’s smaller 55-amp alternator has less potential “reward”.

The alternator’s standard regulator is contained in a housing [aka: “doghouse”] attached to the back of the alternator. There are both “N” [negative] and “P” [positive] types, so named because of the electrical location of the regulator with respect to the alternator’s field winding. They require