Rev counter and speedo playing up

[Warpa1]

Took the 1750 out for a quick spin this evening and both are playing up. Speedo tends to register about 20 mph when i think im going quicker, the rev counter moves from time to time, a tap on the dial and it drops down to 2k rpm when im on tickover

Another thing i noticed that i didnt feel last time out was a type of vibration. While up on the plain i thought i would max it out for a few seconds to see what it can do, the rev note went up but the speed didnt change and to be honest i cant really describe what i felt or heard. The leg was fully trimmed down, half a tank of fuel and me and one other adult in the boat.

it felt a little like my old inflatable with a 4.5hp merc outboard, if i trimmed it up it would over rev and create air pockets? around the prop and lose drive.