Quiet is one of the best features of the A4. They are smooth and quiet. At cruising speed you can carry a conversation without shouting. At idle, you can't hear the motor from 10 feet off the boat. These are benefits that are hard to measure and some would value more than others. Having spent a long windless day on a diesel powered sailboat, I appreciate the difference. As long as Don Moyer stays in business I believe there will be plenty of these little beasts found in the bilges of all those defunct classic plastic sailboats that were built in the sixties and seventies. In terms of dependability and longevity, I think experience has shown that they stack up against anybodies diesel.