Was on the river today fishing a tournament and was loaded down with myself and the co. I was running in to beat the clock and had everything as it was running all day as far as trim and Jack plate. It would run 74 at 5800 rpm, but on my way in the tach was reading 6500, so I backed it down to 5800 and was only running around 55 mph. Could the tach be messed up? The motor runs fine.