My 86 XP 150, model number E150STLCD, looses power at full throttle after getting warm. New plugs, coils, one new power pack, spark on all six and compression good. Had it on the water today. Initially had great hole shot, ran up tp 5200 RPM for about 10 minutes. While at full throttle, rpm dropped to 4000. No more good hole shot, barely dragged itself up on plane.

Any thoughts on what needs fixed? I'm scratching my head.

Thanks in advance for any assistance.

Herman