Are you talking about the hump hose going between the exhaust riser and the muffler ??   Personally I would not want any hose sealed by "gunk" - so I guess I would replace it rather than adding more Band-Aid's.   Take a pic so we can be doubly sure what you are talking about.

Les

Sounds like the hump hose.  Per ABYC standards, double clamps are only required at two paces in a boat: wet exhaust service and diesel tank service.  So, the first thing you might try is to properly double-clamp the hose using marine-grade "T-bolt" hose clamps with locking nuts.  The fact that someone used sealant suggests that there was some trouble in this area, so in addition to double clamping be prepared to replace the hose, maybe even the exhaust riser.  The proper replacement hose for this short segment is blue silicone because of its flexibility.