Diesel engines are built to finer tolerances than are gasoline engines. Theoretically, a well-maintained diesel may last the life of your boat. Since the average recreational boater logs only about 200 hours per year, the 8,000 hour diesel would last 40 years. Although diesels can add considerable cost to a boat, they should be seriously considered because of their durability, economy of operation and safety concerns. Diesel fuel has a much higher flash point than gasoline and does not present the same threat of explosion that gasoline fumes carry.
Engines like to run long and steady.
The shorter the running time between stops, and the longer the idle time between runs, the fewer the hours they will deliver before needing major repairs. The adverse conditions under which marine engines operate have a great deal to do with their longevity. What they really need is rarely what they get. Two of the most important rules of thumb for engine compartment blowers on gasoline engines are that they should always be set to exhaust, not to blow air in, and they should be run for a minimum of 5 minutes before starting the engine. Two indicators that can alert you to potential trouble are the color of exhaust smoke and changes in the appearance of your oil when you check it.