burn

So I'm new to the group... I love my 290 Amberjack but its time to move up because the Admiral wants more space and I want Diesels! Hopefully I can get some advice here. I'm a hobbyist mechanic, but my expertise ends past the dipstick and the wiring harness. We are looking at a 390DA with 700h...

Burned thru the exhaust hose on the starboard riser, starboard engine today. Pics below. It appears to be an actual burn through, not just age-related failure. Engine temperature was normal. Any thoughts on how/what would cause it? 2002 340 Dancer. 8.1s engines. ~ 700 hours