riser and manifold replacement

[76sporty]

(mercruiser 5.7 99', dont know when they were replaced last )when should i replace my risers and manifolds? are these salvageable?

 

[Bondo]

Ayuh,..... Welcome Aboard,..... 1st, you have to clean the castin's to bare metal, to see how much is left,.....

 

[tpenfield]

What @Bondo said. The key factors are water passage and mating surface condition. Clean 'em up so we can see better.