Downsized Surprise

Yamaha remade its popular F25 into a shadow of its former a good way.

Big outboards tend to get most of the ink, but more than half the registered boats in the U.S. are less than 16 feet long, so when Yamaha rewrites the book on its F25, that’s big news to many. Obviously, the weight of an outboard becomes more critical the smaller a boat is, so all Yamaha did is reduce the weight of the lightest version

of its 25 hp four-stroke from 168 pounds (F25B) to 126 pounds (15-inch shaft F25C). That’s a reduction of 42 pounds, or 25 percent, making it the lightest 25 hp outboard on the market, including the direct-injected two-stroke Evinrude E-TEC, which weighs 150 pounds.

The weight loss led Yamaha to reclassify its F25 from a midrange outboard to a portable. Perhaps even more startling is its smaller profile, which makes it look more like a kicker than a main propulsion engine.

One of the biggest differences is the carburetor, or lack thereof. It has been replaced by electronic fuel injection (EFI), a feature that used to require a battery to fire the injectors. Obviously, a battery is still required for the electric-start version, but the pull-start mechanism generates the electricity needed to start it. One might think this adds to the effort required to yank it into action, but thanks to an auto-decompression device, it’s actually easier. It is designed to fire up on the first pull.

I grew up in Wisconsin and drove tiller-steered outboards, so I felt right at home on Geneva Lake in America’s Dairyland aboard an Alumacraft Escape 145 powered by an F25 equipped with Yamaha’s Multi-Function Tiller Handle. This advanced method of controlling an outboard bears no relationship to the tiller handles of old, however. For one thing, I didn’t have to reach back to the engine itself to shift. The shifter’s right on the extra-long handle, which I found provided a more ergonomically correct driving position. At idle, some vibration was transmitted to my tiller hand, but that’s typical of outboards in this class. At every other speed it exhibited minimal vibration, so long runs won’t lead to excess fatigue. And thanks to its rubber engine mounts, the at-idle vibration didn’t cause our test boat to resonate along with it.

Anglers will appreciate the Variable Trolling RPM function, which allows the driver to control the F25’s engine speed in 50 rpm increments, from 750 to 1050 — up to 150 rpm below its standard idle speed of 900 rpm — for the perfect presentation of baits and lures. On the tiller handle model it’s located just behind the shifter; on boats with steering wheels, it can be controlled with a switch on the dash.

Even small boats these days can have an impressive array of battery-draining electronics, so the new F25 puts out 16 amps, which is 14 percent higher than the previous model. And the charging power comes on fast, with the alternator making more than 14 amps at just 1500 rpm.

Transporting the F25 has never been easier, not only because of its reduced weight and size but thanks to an easy oil-retention system that prevents leaks. It can be stored on its side or with the handle tilted up and the motormount side down during transport in the bed of a pickup.

The displacement for the new F25 is smaller, at 432 cc vs. 498 cc, but it accelerates more quickly, according to Yamaha tests on a heavily loaded G3 1448 fishing boat (for which torque becomes really important). It even out-accelerated a Yamaha two-stroke 25 under identical conditions. We purposely ran our performance test on the biggest, heaviest boat of the fleet at our disposal, a Starcraft Patriot 16 SC that had a steering wheel in the side console and was rated for up to a 60 hp outboard. Like the rope-start version, the 20-inch shaft F25 fired up right away and two of us motored away from The Abbey Resort’s marina to open water.

As I jammed the throttle, the Starcraft rose on plane in 4.2 seconds with very little bowrise. Perhaps thanks to the two-cylinder outboard’s “square” bore and stroke of 65 x 65.1 mm, the power curve was very linear. The F25 uses a single overhead cam (SOHC) design, and it took the Starcraft to 15 mph in 8.9 seconds before peaking at 23.2 mph at 6000 rpm. Yamaha engineers wisely designed this engine to be operated for long periods of time at near wide-open throttle (WOT), because most people flog smaller engines unmercifully. According to Yamaha tests, the fuel economy is best at 5500 rpm, only burning 1.9 gph and getting 11 mpg. At WOT, the fuel flow only increased to 2.1 gph, giving virtually the same fuel economy as at 4000 (10 mpg vs. 10.4 mpg).

Look for the F25C to appear on a wide variety of boats, from pontoons such as the Qwest LS 7516 to aluminum fishing boats like the one we tested to microskiffs such as the Hell’s Bay Glades Skiff.