kawabunga

I have a 1997 STX 1100 and it was running strong. I was riding and all of a sudden it started bogging down. the gas was low so I took it home filled it up but it had the same problem. It will rev up as high as you want when out of the water and it will initially plane but it will only do about 20-25, any more than that it just bogs down. one person thinks it is the jets, the other thinks it may have the cooling line clogged but it is pumping water fine. I don't want to start buying parts if someone has an idea what I should be looking for. Thanks in advance.