97 Yamaha Wave venture blowing rubber exaust ?

I have a 1997 Wave venture 760. For the lat two years I have blow out 4 of the hard rubber exhaust tubes coming out of the motor on the side that come out of the back wall. No issue for 11 years. Happens if I am running it hard. If run it hard, it will blow out in about 30 mins. Boat has 155 hours on it. I can run it easy but didn't have to do that for the first 11 years. As you can see by the hours, I don't have it out a lot. Local dealer has replaced part but can't figure out why they blow.
If I put in a stronger exhaust will I take a chance in doing damage to the engine.