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"  Bubbles may make for happy drinks but they don&amp;#039;t make for happy boaters. Propellers aren&amp;#039;t efficient in bubbly water. While your engine is screaming its little pistons out, your boat feels like it&amp;#039;s mushing through a bowl of oatmeal. Just about all outboards route the exhaust through the hub aft of the prop so the prop blades bite into clean water when you&amp;#039;re under way. The problem occurs when you&amp;#039;re in Reverse, like when you&amp;#039;re docking and braking, and you run over your own exhaust bubbles. Low power settings coupled with poor prop bite (cavitation) in slow, precise maneuvering can add up to a real challenge. Yamaha solved this problem on its new high-thrust T60 4-stroke outboard. The engineers didn&amp;#039;t exactly turn off the bubble machine, they just changed its direction. In Forward gear, the exhaust still exits through the hub, but shift into Reverse and those pesky bubbles are redirected through chambers that exit forward of the prop blades. This way the prop bites into undisturbed, clean water in either direction. On the T60, Yamaha combined its exhaust trick with what the company calls a dual-thrust prop--a combination of a high gear ratio (2.31:1 compared with the 1.85:1 ratio on the F60 4-stroker) and large diameter and low pitch (14 x 11 in.). Yamaha claims an increase in thrust of up to 70 percent in Forward gear and 60 percent in Reverse over standard props. The 60-hp 60-cu.-in. &amp;quot;grunt&amp;quot; engine is designed especially for heavy loads such as pontoon boats and nonplaning hulls. The T60 is just one of 13 new outboards in a total of 93 models that Yamaha rolled out for 2003. Unlike some other companies in the field, Yamaha does not contract with other manufacturers to produce its engines. Everything is developed in-house. The company also remains committed to both 2- and 4-stroke powerheads. Yamaha didn&amp;#039;t unleash any big-cube surprises for &amp;#039;03, but it did pull off a small one--a compact, 37-pound, 2.5-hp 4-stroke. Equipped with an automatic decompression device for easy pull starting, this little putt-putt trolls down to 1500 rpm and can scoot a YAM230 boat along at 10 mph. It&amp;#039;s just the ticket for powering canoes, dinghies and inflatables. Features include a splined prop, Forward and Neutral shifting, and a large twist-grip throttle. At the other end of the horsepower spectrum are Yamaha&amp;#039;s 225-horse 4-stroke--a carry-over model--and, saving the best for last, the flagship 250-horse VMAX 2-stroke VZ250 HPDI. This engine is new from the bottom up and should be of special interest to bass boat drivers. At 80-plus mph, bass boats ride on just a few square inches of hull. Add to the equation the tremendous torque of the boats&amp;#039; big-bore engine that tends to skew the hull to starboard, compelling the driver to maintain a delicate balance of constantly correcting the boat and keeping it under control. Slam the throttle shut and the reverse torque will likely hook the boat to port. It is something bass boaters have always had to live with. The VZ250 addresses this problem in a simple but elegant way. The starboard side of the skeg is concave, the port side is convex. The skeg acts as a hydrofoil to counteract torque steer during acceleration, top speed and braking. Up top is a new Hemi-head 3.3-liter V6 that the VZ250 shares with its VMAX VZ225 sibling. The 76\u00B0 block design makes for a compact package and runs forged pistons for greater durability. Feeding this powerhouse is Yamaha&amp;#039;s latest incarnation of its High Pressure Direct Injection system, which operates at 1000 psi for even finer fuel atomization than that of the previous system. Twin high-speed fuel pumps maintain required pressure in the fuel rails, and the injectors themselves open internally so as not to interrupt the fuel plume. This helps prevent carbon buildup on the injector tips. These VMAXes are uncannily quiet, thanks to the engine control module cutting out two cylinders on idle. Additionally, the intake air and exhaust gas run through their own noise-cutting maze. Other good stuff includes a 50-amp alternator and a bypass groove in the bottom piston ring that allows oil to lube the top ring and upper cylinder. With the trend in boating evolving into roomier models (translation: larger and heavier), and consumers wanting boats that go farther and longer, engines will need to provide more power, fuel efficiency and reliability. Once Yamaha&amp;#039;s market research defines specific power output targets, the company plans to up its top of the line entries in both the 2- and 4-stroke categories. Maybe Yamaha will mark the occasion by breaking out some bubbly, which, unlike propellers, makes journalists more efficient.  The VZ250&amp;#039;s lower end features a reshaped bullet to reduce drag.   Twin VMAX VZ250 HPDI outboards make this Grady-White a fast fisher. Engines are quiet and fuel misers. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/adventure/outdoors/a195/1277156/>