I've replaced most of the engine hoses. Gulfstar used the same style hoses thrughout the boat for everything, reinforced fuel & oil exhaust type hoses everywhere. The main 4" exhaust hose (20 feet long) from all ancellary tests (visual, squeeze, etc.) appear fine. I even cut a piece out of one end. Still flexible and strong.

Having said all of that there were a few short pieces of the same hose only smaller diameter on through hulls (below waterline) that were very scary and were replaced.

Interesting how some appear almost new after 30 years while others are completely wasted. Seems like those that are below waterline exposed to constant salt water were wasted while most above waterline are still serviceable.

I would think that backup rubber impellers would have replaced older ones before they deteriorated. My other rubber type replacement parts like those for pumps are still in original packaging. I presume they're still in good shape.