What does this exhaust port photo tell you?

[denhajm]

Getting ready to to a compression test and leak down test on all 6 cylinders. Boat has ran fine for the 3 seasons I've owned it. When changing manifolds this spring I noticed this exhaust port. The center port exhaust port looks to have some deep rust? What does this photo tell me about this cylinder? Water leak in the past? '90 era 4.3L.

 

[Bondo]

Ayuh,.... All it's sayin' to me is,.... Yer manifolds were slightly overdue for changin',.....

Cast iron is quite rough before it rusts,....

 

[Skypirate]

Possibly some perocity in the casting when it was poured, depending which end of the cast was poured, when manufactured, ferris file wax reminant or whats called " investment casting" because you only use it once, the wax burns off as the hot material is poured in sometimes leaving a little residue at the top of pour creating perocity