My 200 merc starts and runs great, but on a long run 5 or 6 miles at 4,800 rpms(55mph) it starts slowing down like I'm pulling back the throttle.If I hammer it, it will jump on up to 70mph like nothing is wrong for a few sec. and slow down. If I stop and let it idle for a bit, it will take off and run another couple miles and do the same thing. If I stop to fish for an hour or so, I can get 5 or 6 miles and it starts slowing down again. No miss, no sputter or anything, it just acts like you are throttling down. I put in a new fuel pump kit but that didn't help. Any suggestions as to what this could be?
