As of block 1B, they can absolutely blast surface craft.
The current Phalanx variant (Block 1B) adds the ability to counter asymmetric warfare threats through the addition of an integrated, stabilized, Electro Optic sensor. These improvements give Phalanx the added ability to counter small high speed surface craft, aircraft, helicopters and unmanned aerial systems (UAS).
As of block 1B, they can absolutely blast surface craft.
https://www.navy.mil/Resources/Fact-Files/Display-FactFiles/Article/2167831/mk-15-phalanx-close-in-weapon-system-ciws/