Phil T wrote:
The engine needs to be mounted so the anti-cav plate is 2" above the bottom of the keel. Typically this is "3 holes up", top bolt in the 4th hole counting down from the top.

The F300 has a WOT rpm of 6000.

Note raising the engine will increase RPM by ~125rpm for each hole raised due to less drag.

This is good because the engine is too low.

Once you raise the engine, re-test and report back.