Many boats, specifically sailboats, come equipped or have have used the 5" case Motorola/Prestolite/Leece-Neville style alternator over the years of production.
This case style alternator today is built by Leece-Neville. They are specifically marinized for ignition protection and are called the 8MR series or marine series. They are available many outputs from 37 to 105 amps and in a 2" single foot, 1" single foot, and single ear and triple ear configurations. The regulators though are all the same design.
The regulators that comes stock on most new 8MR series alternators are voltage adjustable but still only single stage (really a two stage BULK & ABSORPTION) not a three stage regulator thus lacking temp sensing, float modes and a myriad of other features external regulators can offer.
According to Leece-Neville tech support this regulator has an adjustable output range from 13.8 - 14.6 V. It ships from the factory set at 14.2V.
This article will show you how to convert a Motorola/Leece-Neville 8MR style alternator to external regulation. Once you have done this conversion you can then use a Balmar, Ample Power or other external three stage regulator.
My hands down favorite regulators are Balmar. Why? Because they offer more features and control options than any other regulator on the market. The Xantrex XAR regulator is also made by Balmar for Xantrex. I suggest buying a Balmar though because they have some of the absolute best support in the business. In regards to Xantrex customer support, well, let's just say search the net and figure it out for yourself........ You get what you pay for with a Balmar regulator.
This particular alternator is a 90 amp Leece-Neville 8MR2070TA with a 1" foot and triple adjusting ears. It fits many Universal and Westerbeke engines as well as many others.
WARNING: The 90A 8MR2070TA uses a 5/8" keyed shaft and ships without a pulley. Finding and locating a good quality cast pulley in 5/8" shaft can be extremely difficult to find. An alternative to the 90A 8MR2070TA is the 8MR2069TA which uses the more common 17mm shaft. The 8MR2070TA also ships as a 1" foot mount with 1/2" hole and will require a shim spacer (about $26.00) for it to fit a 2" mount. If mounting to a 1" foot you would still need a bolt shim to go from 1/2" ID to 10mm ID or what ever your pivot bolt is.