Repairing 54 yr old rubber exhaust hose 4.125" ID

Ok, but I know the copper is original and it is perfect, no pitting.

My slipmate has a 1983 Tiarra 30 foot twin engine MerCruiser 260 powered. I helped him refit his copper exhaust tubes to new rubber hoses. He has the same copper pipes I have, so they used this successfully for decades in the past. His were in perfect condition too. I rearranged his exhaust design and told him to buy fiberglass exhaust tubing to make the modification. Originally had several sections of cast iron piping which was completely wasted away with rust and was leaking. We replaced all of it with fiberglass exhaust tubing. The copper stayed as it was.

Copper is likely still out there in a lot of older boats and functioning fine.
You must not be very old, or you would know copper was and is still used. Today copper is so pricey that fiberglass tubing took its place.

 

It is said it releases arsenic fumes mixed with exhaust so is not legal on cars here, it sounds better..