90hp Mercury Outboard Over revving

by Joe
(Massachusetts)

I have a 2005 Mercury 90hp 2 stroke Outboard. I noticed earlier this season that the boat was running at higher RPMs than usual and not reaching top speed. I though a out of tune prop. I purchased an identical prop to what was on the boat when running its best and the issue continued. Just the other day on the water I went to accelerate and noticed the RMPs higher than ever almost 7000 and still 10mph below top speed.

The hub and lower unit both seem to be in good working order but I'm not positive how to confirm without opening up the LU.

One thing that I did notice was that my starter drive gear had snapped a couple teeth off. Easy fix... but could this be a cause of my problem??? maybe screwed up the timing?