From Powerboats Reports: May 2004
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Suzuki DF250 vs. Yamaha EFI 250
Suzuki’s DF250 shows you the money, with operating costs 35% lower than older two-stroke technology.
We’re long-term testing a DF250 on our 25’ Contender. Captain Alan Herum has logged 57 hours since January.Everyone knows four-stroke outboards are quieter, cleaner, and more fuel-efficient than carbureted or electronically fuel injected two-strokes. But how much more fuel-efficient? How long does the owner of a big four-stroke have to run his boat to make up the higher purchase price?
We wanted to answer these financial questions with hard factual data, so we put a pair of engines to the test on our Contender 25—a 1998 fuel-injected 250-hp two-stroke from Yamaha against a new Suzuki DF250 V-6 four-stroke.
Performance is another gray area in the two- versus four-stroke debate. The four-stroke still carries the “too big, too heavy, too slow” stigma. PBR wanted to find out how our Contender would handle the extra weight—and just how much slower it might be.
How We Tested
We ran a full performance test on the Contender with its two-stroke Yamaha. After gathering all the data, the engine was removed and the boat refitted with a 2004 Suzuki DF250 acquired for long-term testing. Following break-in, we put the Suzuki through the same performance testing. Weather was nearly identical for both tests. The boat itself, gear carried, the tester, and test equipment were identical.
We recorded speed, fuel burn, and noise levels at 500-rpm intervals, starting at 1000 rpm. We checked and recorded boat speed using a pair of WAAS GPS units. Fuel flow readings were taken with a Navman fuel flow meter. Each setting was held constant for at least two minutes to assure accurate fuel flow numbers. Noise levels were measured from the helm using a Radio Shack digital sound level meter. To negate the effect of wind and current, two passes were made in opposite directions and all readings were averaged.
Because these engines have different operating rpm ranges, we also took fuel flow and noise level data at three typical cruising speeds: 20, 25, and 30 knots.
To conduct an operating cost analysis of these two engines, we calculated the money we’d spend on gasoline, oil, and maintenance on an hourly basis at the three cruising speeds. Any operator can get an estimate of their yearly operating cost differential between the two engines by multiplying the hourly cost figure by the number of hours they operate per year. Those who run their boats over 200 hours a season would have to kick in some extra dollars for maintenance items like fuel filters and sacrificial anodes.
The oil dipstick and filter on the DF250 are easily reached.Base costs used in the hourly calculations were $2 per gallon for gasoline, $15 per gallon for two-stroke oil, and $2 each for spark plugs. Oil change costs on the four-stroke were actual costs we incurred—$27. A fixed ratio of 70:1 was used to calculate two-stroke oil usage.
Performance
Both statistical data and subjective impressions led us to the conclusion that Suzuki’s new DF250 four-stroke is equal to or slightly better than the older two-stroke. A review of the performance charts shows both engines are capable of pushing the Contender to nearly 40 knots.
One performance complaint with some of the new four-strokes is “weak holeshot and lack of low-end torque.” That is not the case here; out of the hole performance seemed better with the Suzuki. No attempt was made to quantify this statistically but rather it’s based on our opinion and experience with our test boat. Suzuki uses a substantially larger prop and higher gear ratio on the DF250 than many older and current production outboards. We think this plays a major role in its powerful holeshot and quick acceleration.
Noise levels on the Suzuki are far lower than the Yamaha at 2000 rpm and below. The difference is most evident at idle—Suzuki 60 decibels, Yamaha 69.5 decibels. Sometimes the DF250’s lack of noise at idle requires us to check the gauges just to confirm it’s running. Once the throttle is advanced, the Suzuki’s lower noise level advantage disappears quickly. From 3000 to 5000 rpm, the difference in noise levels between the two is only a decibel or two.
Operating Cost Analysis
Our hourly cost analysis clearly shows the advantage of the four-stroke Suzuki over the fuel-injected Yamaha two-cycle engine. We calculated the cost-per-hour and percentage savings at typical cruising speeds to arrive with an apples-to-apples comparison. Comparing engines at certain designated rpm settings, as is usually done in engine and boat tests, does not give the complete story. As you can see in our charts, the Suzuki operates 100 to 200 rpm higher than the Yamaha to push the Contender at the same speed. A combination of the DF250’s wider total rpm range, larger prop, and higher gear ratio accounts for this. If we compared performance at rpm settings alone, we would overstate the operating cost advantage of the DF250.
The Suzuki has a 28% to 41% cost advantage over the Yamaha in direct hourly operation at our three selected cruising speeds. The chart below translates these percentages into dollars or cost per hour.
Conclusion
Weight remains a concern of many prospective four-stroke buyers, and we were worried too. No more. The Suzuki’s extra 60 pounds made no noticeable difference in performance or handling on the Contender.
Keep in mind, though, each refit or original installation of a four-stroke outboard needs to be considered on an individual basis to make sure the extra engine weight will not be a problem.
We’ve seen the DF250 Suzuki priced below $15,500 on the Internet, putting it in the same purchase price range as a comparable DFI two-stroke and $500 to $1,500 more than EFI engines. With far lower operating costs than a comparable EFI engine,
the DF250’s slightly higher purchase price can be offset in as little as a year. 
No one is advocating you remove your perfectly good two-stroke and replace it with a four-stroke. (We only did it to gather information on this engine now and more down the line for the long-term test.) But when the time comes for an engine change or when considering power options on a new boat, we do think it’s wise to seriously consider a four-stroke. This test certainly dispels the “too big, too heavy, too slow” notion and bolsters the argument for a four-stroke.
We are generally impressed with the Suzuki DF250 after running it for 57 hours and will publish periodic articles updating this long-term test.
Real World Test: Suzuki 250 4-stroke vs. Yamaha 250 OX-66 
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