Top Highlights

• an engine that is too large will often have to be run at low rpm, a practice particularly harmful to diesel engines.
• The two halves of the shaft coupling must be precisely aligned. Misalignment results in vibration, rapid wear of the stern bearing and, worse, wear of the transmission shaft and bearings.
• one thing to remember is that each is part of an overall drivetrain system and must be matched to the whole.
• In the gasoline engine, gasoline and air premixed in a carburetor are introduced into the cylinders. An electric spark causes the mixture to ignite at a precise time in the piston cycle, driving the piston down in a power stroke.
• In a diesel engine, air in the cylinder is compressed by the piston by a factor of about 20 (the compression ratio). Since the temperature of air is a measure of its energy per volume, quickly reducing its volume by a factor of 20 or more raises its temperature to about 1,000°F. Diesel fuel sprayed into the hot, compressed air ignites, further incr...