Answer
Nov 06, 2025 - 09:39 AM
Isolated ground alternators are mainly used for the purposes of corrosion control. In this scenario current from the alternator does not pass through the engine block and so doesnt contribute to any corrosion of underwater metals. They are only required when the entire engine is set up for isolated ground. Another time they get used is on newer more sophisticated engines with electronic controls. In this case the aim is to remove large currents from the engine block and thus avoid interference with the control systems. Other than those two applications most marine alternators are case ground. This makes them a bit less expensive and it promotes better cooling because the diode assembly can be bolted to the casing and so dissipate heat better. This is covered in more detail in our article An explanation of isolated ground vs case ground alternators.
