Here's a very crude diagram that shows the alternator charging circuit most often found on these early Universal engines. Universal/Westerbeke Corp later changed this dangerous set up, removed the ammeter and jumped the alternator directly to the starter lug. Interestingly enough most of the Westerbeke engines never used a factory installed ammeter and it was sold as an option.
The factory charging circuit leaves the alternator with an orange 10GA wire then most often travels through TWO trailer type connectors to an ammeter at the engine panel. This high amperage current then has to travel all the way back to the battery switch (please not I did not draw the battery switch on this diagram), through more undersized wire, where it finally picks up some larger gauge wire before finally heading to the battery to charge it. These factory circuits often had a 30A fuse in them which was undersized even for some of the alternators shipped on these engines. Owner often put higher amp fuses in or bypassed them all together.
The existing alternator charging circuit, with ammeter, runs as far as 25+ feet on some boats before it gets to the battery banks. On most of these panels the entire current of the alternator runs through 10GA wire and a ridiculous trailer type connector that is a huge point of resistance as these boats age. I have pulled many of these connectors and wires out that were literally melted.
With house power demands getting larger and larger and battery banks getting bigger and bigger, and accepting significantly more charging current, these circuits have been known to literally melt down and in some cases catch fire and this is all with stock alternators. I have seen DIY upgrades to 100+A alternators still utilizing this circuit. PLEASE DO NOT DO THIS!!!