Treq7 - I cannot urge you enough to walk away. Not because the engine has had issues (which is reason enough for concern), but because the 3.0 135hp block lacks power big time.
It just isn't up to the task of pushing the 18ft boat effectively - I've now owned 3 1800's over the years and at worst would recommend the 4.3, at best the 4.3MPI.
My advice is keep looking.....