MerCruiser is calling its 454 MAG MPI Horizon inboard the most important advance in marine power in years because it not only delivers improved performance and efficiency, but relieves the boater of time-consuming service and maintenance.

Using advanced electronics, application-specific components, and a fuel-injection system designed for marine use, the Horizon extends the service cycle on most key maintenance items to an unprecedented three years. The only major maintenance during that time is changing engine oil and filters.

Two key reasons for the reduced maintenance requirements of this engine are the standard platinum-tipped spark plugs, which require only annual inspection, and MerCruiser's constant-tension stainless steel hose clamps, which never need adjusting.

The Horizon derives much of its strength and reliability from the internal components of the heavy-duty General Motors block, particularly the four-bolt main bearing caps. High-flow cylinder heads and MerCruiser's multiport fuel injection and CrossRam intake manifold provide the added horsepower and improved midrange torque. The fuel injection and timing systems are controlled by a proprietary engine-management system that monitors ambient and engine temperatures, barometric pressure, and throttle position and adjusts the timing and fuel systems accordingly. There is also an integral alarm system that monitors engine temperature, oil pressure, and engine overspeed.

For extra durability, the exhaust manifolds and elbows are ceramic-coated inside and out, then electrostatically coated with paint. A freshwater cooling system is standard, and a quick-connect hose attachment mounted on top of the block allows you to flush the engine in less than five minutes.

This review/article originally appeared in Power & Motoryacht Magazine, October 1997 and is written by Ken Kreisler. For more great powerboat reviews, visit their website and subscribe at: https://www.powerandmotoryacht.com/uncategorized/subscribe-power-motoryacht