2 stroke vs 4 stroke
When discussing outboards, it's also necessary to choose between 2 and 4 stroke. The advantages of two-stroke are that they are lighter (for a given power), cheaper, and easier to repair. The advantages of four-strokes are that they consume far less gas than a two-stroke, they are quieter, they don't require you to mix oil in the fuel, and they pollute a lot less. That last point can be very important depending on what your local laws are like. Here in California, some lakes (mostly reservoirs, that I've seen) won't let you on the water unless you have an engine that has at least a two-star CA air resource board rating. Most of these engines are fourstrokes, but also direct-injected two-stroke engines. However, the only direct injected two-stroke engiens I've seen are 50 HP and up, so for your purposes the point is moot. Anyway, a four stroke 8 horsepower outboard is going to weigh in at 85-100 lbs depending on manufacturer. I assume that frogvalley's outboard is a two-stroke, judging by the weight. A 9.9 is going to weigh about the same as an 8 horsepower, so weight shouldn't stop you from getting the bigger engine. Personally, I wouldn't want to lift an outboard weighing much more than 65 lbs up onto my boat every time I take it out. I don't keep my engine on my boat though, so if you would be doing that, maybe the added weight isn't that big of a deal. If you can find a well-cared-for older two stroke, and don't mind the noise or smell, it'd be the best from a performance, weight and cost standpoint. On the other hand, "The California Air Resources Board found that a seven-hour ride on a personal watercraft powered by a conventional two-stroke engine produces the same amount of smog-forming emissions as over 100,000 miles driven in a modern passenger car." Even if an 8 horsepower two-stroke outboard makes 1/20th the emissions of the PWC engine, which is a stretch, that's still a lot of emissions.