I have a fishing friend who readily admits “I never met a horsepower I didn’t like.” And yet in years past I also periodically received letters from older anglers stating that “any outboard with more than XX horsepower just does not make any sense,”—or words to that effect. The size of XX pretty much depended on what part of the U.S. the letter came from. Coastal anglers were always more willing to accept larger engines on the transom than their inland brethren.

Remember way back in the 1980s when Outboard Marine Corporation introduced the biggest outboard to ever hit the recreational boating market? The huge 590-pound 300 hp V-8 “beast,” as it became somewhat less-than-lovingly known by much of the boating public. It was a massive disappointment to many, but to some degree probably because it was a bit ahead of its time. Boats large enough to handle that much transom weight had yet to become popular. And also as a standard 2-cycle, it had a tremendous thirst for gasoline and expensive outboard oil as well.

So, when Suzuki introduced the world’s first 300 hp 4-stroke outboard (DF300) in mid-2006 and willingly let me put my sweaty hands on it, I was curious to see just what they had built. Considering that 4/c outboards are generally much heavier than the old 2/c mills of equivalent horsepower, and also remembering only too well OMC’s 590-pounder of the ‘80s, I expected a real monster. But surprise!! It weighs almost exactly the same as the old OMC 2/c 300. And because this engine employs a 55-degree V-6 block instead of a 90-degree V-8, it is also far more compact.

Although it is only a tiny bit larger, the DF300 is not just a souped-up version of Suzuki’s V-6 DF250. It is actually a completely new design from skeg to powerhead with 4.0-liter (245.6 c.i.d) displacement, as compared to 220.5 cubes for the DF250 (both bore and stroke are larger in the DF300). One of the first boats I tested the new DF300 on was a 36-foot solidly-built deep-V Yellowfin, which had three hung on the transom. My early test numbers revealed the old OMC 2/c 300 of the 1980s did well to get 0.9 mpg at 4000 cruise with only two on the transom of a much smaller and lighter boat. The Yellowfin, however, with 900 21st century 4/c ponies doing the pushing got 1.8 mpg at 42 mph. And at idle each engine burns less than 0.5 gph! You could troll all day on one engine and burn less than 10 gallons of gas. Top speed for this rig was 62 mph at 6250 rpm.

Also to my surprise, acceleration was like a rocket when compared to the old 2/c 300, even with a single DF300 on a 27-foot Key West CC (WOT 44 mph, best cruise 22 mph @ 3.3 mpg and 3500 rpm). Multiport electronic fuel injection does that. Noise levels were way down, too, thanks not only to insulation inside the engine cover, but also engineering of internal components as well. I found it easy to converse in normal tones with my companions, even on the Yellowfin where we were only five feet forward of 900 hp turning 4000 revs.

HOW THEY DID IT

A few years ago Suzuki came up with an offset driveshaft design that places more of the engine’s weight (the powerhead) on top of the transom rather than abaft it. This helps overall hull balance significantly, and so it is also employed in the DF300. At the same time the longer stroke of the pistons reduces their speed somewhat at any given RPM, which in turn lessens stress a bit on all internal load-bearing surfaces.

Other design features include chain-driven dual overhead cams, which operate four valves per cylinder. Variable timing is used for the intake valves to increase power in the upper end of the throttle range, while also maintaining smooth performance at low revs. The DF300 keeps its cool by using some of the raw water from the lower unit intake to also reduce the temperature of the fuel as it enters the manifold.
List price is $23,940 for the 30-inch shaft model. Suzuki Marine, (800) 247-4704; www.suzuki.com.