OX66 RPM Drop Off and Increase

[jeltman]

Having a recent problem with my OX66 250 HP. After getting boat on plane the RPM's drop off 200-300 RPM, and then will cycle back up. Typically run at 4800 28 MPH, engine will drop off to 4600, 4400, and cycle back up to 4800-5000 RPM, without moving throttle lever at all.

Any troubleshooting advice?

[rodbolt17]

clean the vapor separator filter and replace all 3 lift pumps.
your describing a classic loss of fuel rail pressure.
the lift pump replacement should be done about every 3rd season cause the 3.1L motors eat them.