Having 89 Bayliner Capri plane problems

by DaMook

I am new to boating and purchased a 89 Bayliner Capri I/O 2.3 Ford engine.. I took it out on the lake about 4 times and it ran like a charm all day long. I then took it out another 2 times and it ran good and got on plane pretty fast, until I got to my fishing hole and let it sit for awhile. On the way back to the dock it would not plane and appeared that the back end was really low in the water and it took me about 3 times longer to get to the dock. I did not change the tilt at all from where it was, so im not sure what the problem could be. If anyone has an idea of what it could be, please let me know.