1987 Johnson GT150. Mod # J150GTLCUR Serial # R 7566081 Compression is 80 across except 1 was 70.

This happened to me once last year, then never happened again so i thought nothing of it. Now it does it everytime. When i am at WOT the motor will surge, and lose about 5mph, hear a noticable difference in the rpms, then go back to running fine. Its completly random, sometimes it does and doesnt do it. Also this could be a different problem, but i noticed it dogs a little more getting on the trailer and getting on plane. So far i have changed the fuel filter, plugs and wires. no change at all. Anybody have any suggestions?