If you slow the speed down by half, does it still stutter?
How deep are you cutting at 80ipm, and what type of bit are you using.
There really is no general speed rule for a given size tool,because different types of tools will cut differently.
On our 10HP router, I'll cut oak or maple hardwoods differently depending on the tool. The following are all 1/2" bits.
With a single flute indexable cutting bit (Amana), I'll cut about 3/8" deep per pass, 17,000rpm and 120ipm.
With a 2 flute spiral, up to 3/4" deep per pass, 16,000 rpm and 150 to 200 ipm.
With a 3 flute chipbreaker spiral, 3/4" to 1" depth, 15-16,000 rpm, 200 to 400 ipm.
Sharpness makes a BIG difference in speed. Also, climb cutting may be necessary depending on grain direction.