I don't about the rpm but it does looks like you might need a flat bottom boat. During the Spring my yard looks like that but it cover 6 acres. I have been threatening to buy myself a scuba diving suit so I can get to my shop on some days.
As the rpms you need to be checking it with a tach as it may be very well beyond 4000. Most of the Briggs around here are running around 3450
