Features June 2007 Issue

9.9-horsepower Outboard Engines Put to the Test

With little difference in performance numbers, the best choice for a large, short-shaft dinghy engine really comes down to features and what fits your needs. We tested the 15-inch shaft Mercury 9.9, Tohatsu 9.8, and Honda 9.9, each of which could also be used as a sailboat auxiliary engine. Weíre waiting for Yahama to release its re-designed 9.9 h.p. outboard engine to test it along with the Suzuki 9.9 for an update to this 9.9 outboard engine shootout.

Todayís 9.9-horsepower four strokes pack just the right amount of punch for a portable dinghy engine. The downside, as you may have guessed, is their hefty weight. The three Practical Sailor tested range in weight from 82 to 92 pounds. All are two-cylinder, water-cooled engines that take about a quart of oil, and all are pull-start models, with chokes that need to be used only when the engine is cold. All come with a standard 3.1-gallon plastic fuel tank, a fuel hose, and an aluminum propeller. In terms of propulsion, none of these portable outboard engines has it all. So after evaluating how easy each was to operate, transport, store, and maintain, we based our recommendations on weighing each engineís pluses and minuses.


9.9-Horsepower Engines
A calm Sarasota Bay, Fla., provided ideal conditions to test the 9.9-horsepower engines. The Tohatsu, pictured here, is nearly identical to the Best Choice Mercury, but has fewer features that testers liked.

Some cruising sailors may be content with a dinghy that barely moves, one propelled with muscle and a pair of oars or a super-small outboard (see Practical Sailor December 2006). But when you pack a little boat with a few people and supplies, this amount of power&emdash;whether human or horse & emdash;just doesnít cut it. A larger outboard delivers the necessary oomph to move your crew and goods from boat to shore&emdash;and back&emdash;in a timely, safe fashion.

Todayís 9.9-horsepower four-strokes pack just the right amount of punch. An 8-horsepower four-stroke (Practical Sailor Jan. 15, 2004) may still struggle with a fully loaded boat, while a 15-horsepower motor can border on overkill, as many inflatables and rigid hull inflatables (RIBs) can become squirrelly and hard to control when pushed too fast.

The downside, as you may have guessed, is the weight of these engines.

Practical Sailorís trio of test motors range from 82 to 92 pounds, so weíre not sure why some manufacturers classify them as "portable." Wrestling these behemoths on and off our dinghy was a back-breaking experience.

What We Tested

Practical Sailor

secured three engines for dinghies: the Mercury 9.9, the Honda 9.9, and the Tohatsu 9.8&emdash;all 15-inch, short-shaft models. We were unable to find a Suzuki 9.9, but we plan to test one in the next few months. Yamaha declined to participate in this test because the company says itís coming out with a re-designed 9.9. Again, we plan to test and report on this engine when it becomes available.

Practical Sailor

tested the trio as dinghy engines, but many of our findings regarding the short shafts & emdash;ease of starting, throttle control, maintenance access, warranty, etc.&emdash;should be useful for sailors looking for an auxiliary (long-shaft) model.

What We Found

All of these two-cylinder, water-cooled engines take about a quart of oil. All are pull-start models, with chokes that need to be used only when the engine is cold. All come with a standard 3.1-gallon plastic fuel tank, a fuel hose, and an aluminum propeller. Tohatsu and Mercury back their engines with a three-year warranty; Honda recently increased its warranty to five years. All of the engines carry the highest emissions rating: three stars.

Honda, Mercury, and Tohatsu also offer these motors with electric-start and/or power-tilt control. The Honda is the only engine in our test group with a standard 6-amp alternator. An alternator is optional on the Tohatsu, and the Mercury Big Foot 9.9 model comes with an alternator with a 6-amp capacity.

The Honda is by far the heaviest and the most expensive engine in the group, weighing in at just over 90 pounds with a retail price of $3,003. The Tohatsu is the lightest (81.5 pounds) and least expensive ($2,067 retail). The Mercury comes in at 84 pounds, with an MSRP of $2,595.

What about street prices? Defender Industries, which specializes in small outboards, sells the Mercury for $2,086, the Tohatsu for $1,773, and the Honda for $2,337.

Shifters and Stop Buttons

The Honda and Tohatsu gear shifts are on the forward section of the engine, but Mercury integrates the shifter into the tiller handle. This is a nice feature, in our opinion. There is one minor downside with Mercuryís "shift in the handle" feature, according to

Practical Sailor technical consultant Erik Klockars. "Some owners have said that when their hands are slick with oil or sunscreen, it becomes difficult to move the throttle in and out of its detents." One tester, whose hands were drenched with sunscreen, did not have a problem.

The Mercury is also the only engine to mount its stop-engine button on the throttle face, keeping the driver from having to turn around to find it. The Tohatsuís stop button is aft on the engine face, while the Hondaís is about a third of the way down the tiller. All three have tillers that extend 18 inches from the transom.

Maintenance and Storage

As with most four-strokes, the engine oil for all three of our test engines must be changed after the first 20 hours of operation and then after every 100 hours of operation. The Mercury and the Tohatsu do not have oil filters. The Honda does, and access to it requires removing a panel cover on the starboard side.

All of these engines must be stored in specific positions to prevent the engine oil from entering the cylinders. The Mercury and the Tohatsu must be stored on their tiller (port) sides on the elbow portion of the tiller, making them less stable when stored than the Honda, which is stored on its non-tiller (starboard) side.

All three engines have "bumps" on the cowling that they rest on. It would be nice if those bumps were covered with rubber for protection and to help prevent movement during storage.

Flushing these engines with fresh water plays a major role in long-term durability. All three manufacturers offer a flushing attachment. The Honda has a flush port on the powerhead, while the flush port on the Mercury and the Tohatsu is on the lower unit.


The Honda is the toughest engine to transport due to its weight and the location of the carrying handle on the front of the engine. This plastic handle is mounted at the top of the transom bracket between the two clamp-screw handles. The swiveling bracket, even when in its tightest position, can still move when you pick up the engine by the handle.

We prefer the aluminum front carrying handles on the Tohatsu and the Mercury because theyíre larger and welded to a non-moving portion of the engine.

On the plus side, the Hondaís aft cowling latch is much beefier than the Mercury or Tohatsuís plastic latches.

Testers said the Honda was harder to raise and lower than the other two engines due to its greater weight. The tilt lever on the starboard side is big and easy to find. The lever that adjusts engine-rotation tension needs to extend farther forward so itís easier to reach and adjust. On the plus side, the side-mounted flush port makes it the easiest to flush while its still on the dinghy.

Testers also thought the shift lever on the Tohatsu moved more smoothly than on the Honda.

The indicator on the throttle that tells you whether the engine is in the start or acceleration setting needs to be more prominent, in our opinion.

On the water, the Honda pushed our dinghy to a top speed of 15 knots, which was a full 2 knots slower than both the Tohatsu and Mercury. But the Honda was clearly the quietest engine overall, registering only 62 decibels at idle and 87 decibels at 10 knots.

The Honda racked up the best fuel-burn numbers, too.

Bottom Line:

Itís heavy and falters in some ease-of-use areas, but the quiet-running Honda, with its standard alternator, should be considered for an auxiliary engine.


At 84 pounds, the Mercury is the middleweight in our test group. With its large front carrying handle and recessed area below the cowling on the back, you can get a good grip on it for lugging it around. The Mercury could use some larger bumps (like on the Honda) for port-side storage.

We had some difficulty figuring out how to operate the tilt release-lock mechanism on the Mercury. To raise or lower the engine, you must make sure the throttle is in the forward position and the release-lock button is in its unlocked position. To lower the engine, the button must be moved back to the unlocked position and the engine must be tilted all the way up; this releases the lock and allows the motor to drop.

The Mercury did well on the water. It tied the Tohatsu for best top speed (17 knots), and noise levels were equal to or very close to the Hondaís.

Bottom Line:

The Mercury has a lot going for it. We like the gear shifter in the throttle and the easily accessible stop button. Itís about as light as the Tohatsu, and its fold-down throttle makes storage easier. Itís Practical Sailorís top choice.


The Tohatsu is a few pounds lighter than the Mercury, and it has 9.8 horses rather than 9.9, but the power difference is negligible. Even though the Tohatsu and the Mercury are essentially the same engine, the Tohatsu lacks some of the features that make the Mercury easier to operate, like the shifter in the handle. But it also suffers from the same shortcomings that we cited about the Mercury (flimsy aft cowling latch and tiller-side storage).

Another difference between the two is the design of the tilt-release mechanism. The Tohatsuís lever is located on the starboard side. The lever should be bigger, but

Practical Sailortesters had no problem releasing and locking the engine.

The Tohatsu was the loudest engine of the three, with a wide-open-throttle decibel level of 92 and 90 decibels at 10 knots. At idle, it was in the same ballpark as its competitors. Fuel usage and top speed were identical to the Mercury.

Bottom Line:

The Tohatsu lacks some of the attractive features found on the Mercury, but itís significantly less expensive than the other two engines. Itís our Budget Buy.


None of these engines has it all, so our recommendations are based on weighing their pluses and minuses.

We would not recommend the Honda for those who anticipate having to mount and remove the engine from the dinghy frequently&emdash;even if you plan to use a halyard and winch for muscle. Itís too heavy and cumbersome&emdash;and that plastic handle makes it even more difficult to move around. Weíd recommend the Honda for permanent installation, however. Itís quiet, fuel-efficient, has standard charging capability, a five-year warranty. And donít forget about Hondaís reputation for durability.

If you anticipate using your dinghy a great deal, weíd seriously consider the Mercury, our Best Choice. Itís the most user-friendly engine in our group, provides peppy performance, and runs quietly.

If you want to save some money and donít care about the location of the shift or stop button, the inexpensive Tohatsu is a no-brainer.

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