I'm looking at buying a 1985 Sea Ray 260 Weekender. It seems to run
fine, however it has the original 260 HP Mercruiser engine. I've been
told that because it has been in salt water its entire existence, and
it is now 20 years old, I should assume that I will need to replace
the engine within a couple of years (manifolds and risers have been
recently replaced).

The boat is in great shape, includes a trailer, and is selling for
under $10k. At that price, it appears to be a great deal, but I
suppose I have to add in the price of an engine replacement to get a
truer picture.

I'm curious what anyone's take is on the life of a salt-water cooled
engine, and what the average cost to replace it might be.

Any input would be appreciated.