I recently purchased a 2008 Sunesta with 80 hours on the Mercruiser 5.0 engine. The problem I am having is that it won't plane out if anyone is sitting in the back seat. I was thinking just changing the plugs, wires, filters, and oil might help but I'm not sure. If I put 4 adults up front and two in the captains chairs it will plane out okay but not great. Shouldn't this take off with no trouble only carrying 6 adults (two up front, two in captain's chairs, and to in backseat) with 3 kids tubing?