Your boat may be straight out of the factory, but it’s already taken two hits when it comes to efficiency. Marine engines generally run at or near peak RPM for extended periods of time under heavy load conditions, according to outboardrepairs.com; every time they have to make it through a wave or a wake the engine has to strain to keep the RPM constant. Also, an extended period of time between uses is extremely common when it comes to boats, which allows for damaging corrosion to build up quickly.
But these demanding conditions can be combat by keeping your engine properly lubricated with oil such as Yamaha 2m oil. A high-quality oil will reduce fiction and leave the cylinder walls properly coated to eliminate corrosion between uses. Changing the crankcase oil frequently will also prolong the life of your engine.