Big alternators require substantial air flow to keep them cool.This requirement is often at odds with the need to protect the drive belts.

If the alternators do not have good air flow their efficiency drops and the diodes, bearings, and windings lead a hard and relatively short life.

This is not as big an issue if you are using alternators with remote diode assemblies (as we are on the FPB 64s), but it is still a concern.

Most engine manufacturers have tight belt guards which cut down on cooling. In a yacht with a small battery bank and light DC loads you can get away with this. But not with bigger systems if you expect long alternator life.

Circa’s elegant solution is shown in these photos. There is visual openness for cursory inspection, and good air flow.