Just back in from the water, Same thing

Won't go over 2500??
Disconnected the tan wires and it had no effect
Oils has been disconnected for years so I am sure there is nothing there.
Tied to a empty mooring and cked things out, motor starts and runs great, raced the engine in neutral and it gets full throw and full rpm's, but as soon as you put in gear and load up the motor its still at the 2500??
Why is it for the last few years I get half way threw the season and bam I get screwed??