I need some help, I have a 2003 24 ft sea ray sundancer with a 5.0 mercrusier. last weekend I loaded up the boat with people and gear and set out to enjoy a day on the water, but when I set out I could not get above 12.5-13 knots, no matter how I trimmed the boat it just would not go, yesterday I took the boat out again and had 5 people on (I had eight before) and again it just would not go, so we decided to just head up the river and stop at a resturant and get some lunch, after about 15 minutes the boat began to pick up speed and after we had lunch we headed back and every thing worked like a champ, it did this last year a couple of times, and I changed the fuel/water seporater and it did not seem to help. it is almost like something is clogging and some how works its way through, but on ocassion the problem returns, the boat never spits and sputters, it starts fine and even when I go full throttle it seems like it wants to go but it just stalls around 12-13 knots,