Well but not very well ... but with the small 4-strokes, unfortunately, that's the way it is.
I rate the product 3 and a half stars, coming from an old 2-stroke 4 hp twin-cylinder Johnson (same displacement as this 3.5 hp single-cylinder). Let's say that the 2-stroke is somewhat regretted in some respects. I summarize the pros and cons of this small 3.5
PRO
1) truly ridiculous consumption. On average it consumes half of the old 2-stroke 4hp twin cylinder of the same power. With 5 liters of petrol I can do 10 hours of towing with an average speed of 4 knots.
2) essentiality. What is not there does not break, says the proverb. This model does not have the timing belt, oil filter, injection. It has very simple mechanics.
3) yield. It pushes really well.
4) WEIGHT. Virtually the only 4-stroke on the market with adequate power for trolling with fiberglass boats and a weight that makes it transportable self-beach. Let's say a compulsory purchase, in my case, for this very reason.
VERSUS
1) Absence of fuel pump which prevents installing the external tank even after the warranty. On the American models, however, the pump is there. Totally rejected this Mercury policy. Do not waste time researching models sold outside the US, the petrol pump does not exist. Fortunately, consumption is negligible, but refilling in the middle of the sea is not ecological and is very annoying.
2) Vibrations. The engine vibrates being a single cylinder, and transmits the vibrations to the boat more than my old 4cv johnson. Bothersome.
3) Noise. It is noisy, you can hear the noise of the mechanics without timing belt. It is metallic, impulsive noise, really annoying. It is improving a little after the break-in, but for hours and hours it is annoying. Consider purchasing a more powerful model which should be less noisy (if you can manage its weight). I use cell phone earphones and recommend them for extended engine use.
4) Plastic propeller. They could have tried a little and at least put in the metal propeller. After all, we are talking about a thousand euros for an engine ... Also in this case, the Mercury policy is no longer valid.
Would I buy it back? Yes ... for me, I repeat, it is an obligatory choice due to the weight. But I regret my old 2-stroke a little ... To evaluate the 4 horses, but they are 23 kilos against 18.