Buried deep in your engine compartment, running under your decking, or winding from an invisible exit pipe to a pump, they're part of a system that keeps your boat running right and safely. For this reason alone, they warrant regular inspection and, when needed, rapid replacement. Your exhaust system is constantly subjected to massive changes in temperature. This is particularly true of wet-exhaust systems, where water is used to cool the hot gases from your engine.
Rubber is more flexible, and is able to stretch and shrink repeatedly.
However, it will eventually weaken and split. Silicone hoses are considerably stronger, and can last six times as long. They are much more expensive, but we think they're worth it. Fitting a pricey hose may seem pointless, but it will save you money and hassle in the long run. Vibrations from the running engine can shake the clamps holding the various pieces of hose together.