95 Mercury Sportjet 120HP Issue

I recently purchased a 95 Sugar Sands Mirage jetboat this is powered by the Mercury SportJet 120HP Engine. Ive had the boat out a few times and have encountered the same problem each time. The boat starts right up and runs awesome for the first 30 minutes that im out. After roughly 30 minutes of using the boat, the motor begins to hesitate!! It doesnt stall out, just hesitates when I try to gas it. It still picks up speed, but seems to hesitate every second as it speeds up. Im not sure if its an issue once the motor heats up, but Im just hoping for some ideas on what could be wrong with it. After the first time this occured, I replaced the spark plugs thinking that it could have been a fouled plug, but the issue occured again. Not sure if it could be the Spark plug wires, Coil, fuel filter, etc... If anyone has some tips for me, Id appreciate it. Thank you!!