60hp Mercury motor feels like its dragging

by Mike
(Michigan )

When i go full throttle, for about 2 minutes, it feels like my motor is dragging. Won't get to full speed, then all of a sudden, without really doing anything, it kicks in and goes full speed. Probably at least a 10mph difference. Then again all of a sudden less than a minute later, it starts dragging again. Not a huge noise or rpm difference. Just a much smoother ride and more mph.

Any help would be great.

thank you!