Today’s four-stroke outboards are more reliable than ever before with fly-by-wire controls and onboard sensors that maximize performance and efficiency. But, as my Roman forebears used to say, caveat emptor: The four-stroke solution is not the singular magical fix ideal for repowering all boats. What boats are we talking about? What are the challenges? What should you do before repowering?
Here’s the scoop.
The first generation of four-strokes all had one thing in common: They were heavy. When you added all of those extra four-stroke parts, like an oil sump, valve train, etc., the engines definitely increased both their mass and weight. For example, the Yamaha F200/F225 four-strokes weighed more than 600 pounds (and they still do today at 608 pounds). A 200 hp two-stroke engine of that era might have weighed 425 pounds.
In 2014 just about any maker’s 200 hp V-6 costs upwards of $20,000 installed, depending on your gauge package, controls, installation, etc. Although it doesn’t burn pricey two-stroke outboard oil, it does require additional maintenance, like oil changes every 100 hours of use and valve adjustments at every 300 to 400 hours, expenses that don’t impact two-stroke owners. (For a complete breakdown of the cost of outboard ownership, visit boatingmag.com/boatinglab-outboards.) Plus, four-strokes that deadhead half of their cylinders with every turn of the crankshaft need more cylinder mass to compete with the prop-shaft sea horses generated by two-stroke power plants that are firing all of their cylinders with every rotation of the crank. If you are repowering a newer boat, going with a four-stroke repower is probably nothing to worry about. But when considering a new outboard for a pre-2002 vessel, there is a concern regarding which solution will work best, since these boats likely weren’t designed with the requisite buoyancy aft that is needed to keep cockpit scuppers above the waterline with added weight on the transom.
If you have to stick with a two-stroke due to either weight or mass, Evinrude E-TEC and Mercury OptiMax two-stroke direct-injection V-6s should do the job. Sure, you’ll have to buy some two-stroke oil in bulk, which adds to the cost-per-mile of boat operation, but you’ll never have to do an oil change, swap an oil filter or adjust valves, all of which add to annual operating costs.
Also, four-strokes are losing weight, which should help when repowering an older legacy boat. Yamaha recently introduced an in-line 2.8-liter F200 that tips the scales at a svelte 487 pounds, which is actually lighter than a two-stroke 3.0-liter V-6 OptiMax. Not to be outdone by the competition, Merc introduced its own next-gen four-stroke last year, a 150 hp — an in-line-4 with a 3.0-liter block that has room to grow. It tips the scale at 465 pounds. The valves on this new Merc 150 never need adjustment, which will lower operating costs.
If you need to focus on outboards in the 225 hp to 300 hp range, Yamaha’s new-wave Offshore series (225, 250, 300 hp) provides the power and torque of a 4.2-liter V-6 block but lowers the overall weight of these triplets to an incredible 562 pounds. This mechanical miracle was accomplished by taking out the six-pack of steel-cylinder liners, which opened up the bore volume, which was then plasma-infused to provide a superslick surface to reduce piston-ring friction. I have personally tested all three of these new lightweight four-stroke outboards in single, twin and triple configurations on both new and older boats, and they are indeed next-generation masterpieces that will afford you with some viable repowering options.
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