Hopefully, someone can point me in the right direction with a little problem. I have a 454 Mercruiser with Bravo III drive and recently I noticed at low rpm (about 1,000 or so) it kind of felt as if it was caught on something (it wasn't but it's the only way I can describe it) and the rpm would drop a 200 or so, then a few seconds later it would rise back up. <br /><br />The problem seem to disappear after I attained cruising speed. <br /><br />Today, it was doing it at cruising speed and dropping 500 or so rpm then a couple of minutes later would rise back up. <br /><br />On the return trip I noticed that it seemed to have a lost a lot speed too. At 4,000 rpm I was only doing 25 knots, when usually I would be doing 32 knots or so. Also, it needed about 3700 rpm to plane, usually about 3000. <br /><br />Before I call in the mechanics is there anything obvious that could be causing this? All oil levels, batteries, etc, are fine. <br /><br />Many thanks for any help.