Boston Whaler Jet overheating

[CowboyEckols]

I have recently acquired a Boston Whaler Jet from a good friend of mine. He says that it has had overheating problems from the time he bought it. The last time he took it out he said that it over heated shortly after putting it in the water and he never messed with it again. Any ideas on what would be causing the over heating. I have already pulled the prop out to make sure it wasn't clogged. But, Beyond that I haven't messed with it much yet.