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Mercury 9.9 Outboard Motor

A Second Generation 4-Stroke Boasting a Light Weight

Mercury Marine's 9.9 horsepower four stroke small outboard motor.

This review is based upon a two-year evaluation of a production 9.9 Mercury, four-stroke outboard motor. More than 300 hours were logged. The 9.9 was run every day on my Mercury inflatable dinghy for at least ten minutes. Suffice it to say I got to know this motor very well.

In the very beginning I did not like the way the throttle and shift were incorporated into the tiller arm. Frankly, it felt clumsy. The reason was as simple as salt: I had grown up on the Mississippi River running Jon boats rigged with Evinrude 18-horsepower outboard motors. Those venerable, old two-strokes had the throttle on the tiller arm and the shift lever on the other side of the motor. Over time I got used to it the Mercury set-up. You probably will too.

I really like the way the engine can be tilted out of the water with just one hand. Other brands require two hands. My friend, Howard, who lost his right arm in one of our nation's war, had a difficult time until he converted to Mercury outboards. To tilt the Mercury 9.9, put the engine in forward gear, grab the back of the cowling and life.

I also like the way I was able to so easily clear water out of the carburetor float bowl by removing the cowling and opening the drain screw in the bottom of the bowl. I made life easier by adding a Racor filter/water separator specifically designed for small outboard motors. Since I installed one my water-in-the-fuel problems have nearly disappeared (Part # 025-RAC-05).

Truth be told the engine is a little cold-blooded. Even in 90-degree weather it needed a couple of pumps on the engine-cowling-mounted primer bulb and full choke. Once warmed up, by playing with spark plug gap and the idle setting, I was able to get idle speed so slow the 9.9 tick-ticked like my grandfathers old watch.

After the first 20 hours, and about every 50 hours after that (the owner's manual says 100 hours), I changed crankcase oil in a clean-hands, environmentally safe manner. With the engine warmed and all the nasty stuff in suspension, I poked the wand from a Moeller vacuum pump into the dipstick hole and sucked it all out. This engine does not have an oil filter like the Mercury 9.9 BigFoot. I also used the Moeller pump with an oil-fill pump fitting spliced onto the end to change gear oil.

I priced common repair parts, things like impellers and carburetor-to-intake-manifold gaskets and they are reasonably priced.

Performance was great. Acceleration was razor-sharp thanks the carburetor's accelerator pump that splashes extra fuel into the combustion chamber. Most outboards don't have one.


Racor's fuel water separator filter for small outboard motors 025-rac-05

Add a filter/water separator specifically designed for small outboard motors to the fuel system and water-in-the-fuel problems will likely disappear.