Engines — By
Patrick Sciacca — January 2001
|Part 2: Technology is only as good as what it’s attached to.|
Although there is a significant horsepower difference between the two engine versions, they have many similarities. Both have roller hydraulic camshafts for minimal friction and canted valves for optimum breathing. Both come with long-life platinum spark plugs. And both can be rigged by OEMs with an electronic throttle kit from GM that enables fly-by-wire operation, similar to what’s available on many diesels. This means the only thing connecting the engine controls to the engine is an electrical cable, a feature that makes for not only easier rigging but also easier operation. Moving through the rpm range is generally smoother with electronic controls, and synching engines can be done accurately and automatically. Moreover, fly by wire opens up a world of electronic networking possibilities with equipment such as autopilots and GPS navigators. Also standard on both engines is a new coil-near-plug ignition system that increases ignition energy by 50 percent, improving reliability (there are no moving parts), increasing fuel efficiency, smoothing idle, and reducing emissions. GM’s fourth-generation ECM (electronic control module), the MEFI IV, is available to marinizers (some have their own processors) and includes a more powerful computer to more accurately control ignition timing and fuel delivery. Even the firing order has been carefully selected. It’s 1-8-7-2-6-5-4-3, a sequence GM says fires more evenly and so reduces stress on the crankshaft by seven percent.
But technology is only as good as what it’s attached to. The standard and high-performance 8100s start with a durable cast-iron block and cylinder heads. An integral positive crankcase ventilation system is designed to trap pollutants before they escape into your bilge, and a coated, cast-aluminum intake manifold maximizes air flow to the injectors to increase mid-range torque. The water pump used on both engines has a bronze impeller and is silicone-carbide-sealed to extend life in the saltwater environment. In addition, the Vortec 8100’s bottom-end and oil-pan designs allow for installation at a multitude of angles, allowing it to easily fit into most engine rooms.
There are differences between the standard and high-performance engines as well. The 375-hp Vortec V-8 comes in at 732 pounds, while the high-performance engine weighs eight pounds more, a difference attributable in part to their crankshafts. The standard 8100’s is made of high-density nodular iron, while the high-performance engine’s is forged steel, which is better able to handle the engine’s increased output. Both engines’ crankshafts are internally balanced, which means there are no external counterweights, resulting in reduced stress on the crankshaft and bearings and a more compact envelope.
Finally, and of prime importance to boaters, both versions of the 8100 were engineered with an eye toward durability. In fact, GM’s marine-engine standards surpass those required for its truck applications. In one test the engine was run in 60-minute cycles‘wide-open throttle for 55 minutes, then idle for five minutes‘nonstop for 300 hours, far exceeding the use the engine might get under normal operation.
Now that GM has researched,
engineered, built, and tested the basic engine package, OEMs such as Crusader,
MerCruiser, and Volvo Penta are adding their own bells and whistles, such
as proprietary ECMs, exhaust manifolds, fuel/water separators, and auxiliary
pumps. (See “Primping Iron”, this issue.) So if you’re
looking for a gasoline engine that offers a tradition of excellence, the
newest technology, and saltwater toughness, GM has your V-8.
This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.