Maybe put something "over" the muffler area and see if the salt
accumulates on the "shield" or only on the muffler underneath the "shield."
- - New exhaust
hose can contain pinholes or other "fracture or punctures" which occur when they are improperly handled during shipment from factory to the end seller. I had a brand new length of 4 inch exhaust
hose with a thumbnail shaped tear in it that opened up when the engine
was at cruising power. Made a horrible mess in the engine room spraying hot exhaust salt water