I have a new 2.5 hp 4-stroke Mercury outboard motor on a 12-foot aluminum boat:
I've used the motor four times; 15 km per trip.
When I first got the motor, it seemed to have a lot more power at full throttle. Now, there seems to be significantly less power.
I don't think the difference in power is all in my head: Previously, at full power/throttle, the motor only got about 1 km to a tank (the tank is small and built into the motor). Now, at full throttle, there is less power, and I can get 10+ km to a single tank on full throttle. So the fact that I now get 10x fuel range at full throttle is evidence that it's not operating at full power.
Notes:
- The motor has oil in it.
- I use supreme-quality gas.
- The weight in the boat hasn't changed and the conditions haven't changed -- I only boat on calm water, on the same lake in the same place, with minimal gear.
- The motor's shaft is tilted so that it's perpendicular to the water (straight up and down when in operation). I believe that's the correct angle.
- When initially breaking in the new motor, I followed the manufacturer's instructions (reduced throttling for specific durations).
- Here's a photo of the spark plug condition (click to zoom in):
As a novice, I'm wondering why I no longer have full power/speed at full throttle.
