I have no idea of how many hours my engine was run like that before I bought the boat. It took me a while to realize that there was a problem. The engine would overheat if it was run above 1800 RPM
for any length of time. When I discovered that the salt
water was displacing the fresh, I replaced the end rubbers on the exchanger, but it made no difference in the over heating. I continued to use the engine with a self imposed 1800 RPM
limit for the eight years that I owned the boat. That was enough horse power for me. When I sold the boat, I told the new owner about the overheating
and he wanted more power, and ended up pulling the cylinder head
and finding all of the cooling
passages clogged with salt and rust. That is the real danger
of salt in the system (rust and percipitation). If you dont have any heating problems after the exchanger is fixed, then just run some of the coolant system cleaner through it and dont worry too much about it.____Good Luck.____Grant.