Friend has a 2014 Evinrude Etec 115 horse on his boat. At wot it goes about 38 mph according to the speedometer and fish locaters GPS. At wot of 38 mph after a few mins it usually throttles down on it’s own to about 36mph for no reason. If you throttle back and then throttle up to wot again it goes back up to 38mph. If you don’t it will just keep going at the slower speed.
Whats going on here?