What a wild ride it's been. During the last decade of the 20th Century, marine engines made great advances. First came electronic engine management systems that fine-tuned ignition spark to optimize performance at the same time they protected against the ravages overheating and low oil pressure. Then came electronic fuel injection (EFI) which brought easier starting hot or cold, a smoother idle plus modest gains in fuel economy. Direct Fuel Injection (DFI) transformed the personality of two-stroke outboard motors, lending them razor sharp acceleration and miserly fuel economy. So what sort of marine engine technology might we see in the near future?
Look for a greater proliferation of ceramic-coated piston domes and combustion chambers. They'll raise horsepower levels all the ay up and down the rpm band by preventing heat (energy) from escaping through the coolant. Simply put, a greater number of BTUs released during combustion will be made to do work. As a result fuel economy will improve, so too will acceleration.
Further enhancements will come through the even more sophisticated application of microcomputer control. Engineers are already busy in emissions labs mapping fuel flow and ignition spark timing to better match operating conditions. At least one team in white lab coats has already replaced conventional spark plugs with laser beam plugs. In some cases research has progressed beyond prototype into the real world production motor. Case in point, Suzuki outboard motors offered a production ceramic V-6 outboard motor back in the mid-80's.
This gives rise to the salient question: Are we poised for a proliferation of marine engines fitted with ceramic parts? The answer depends on economy of scale, whether or not the cost of tooling up will be low enough for the limited production of boat motors.
Beyond hardware, look for big advances in petro chemistry. What if gasoline and lubricant were the same fluid? Or, if right out of the pump gasoline molecules were 10 or 20 micron, the optimal size for clean burning. Stay tuned.