The Ultra models are designed for larger, more spacious sailing boats and motor yachts. They have a heavier three- or four-cylinder diesel engine that powers an alternator with two coils and four poles. This low speed means the Whisper Ultra is both very quiet and, due to reduced wear, requires even less maintenance compared to the high revolution models. This is an ungrounded generator, suitable if you have an aluminium or steel vessel and wish to prevent electrolytic damage