Yikes, that's good to know. None of the Alolachu I've fought so far ran Surf, so I never knew that was a danger.I want only to underline that Alolan Raichu (a strong Electric Terrain abuser) has Surf in order to get past this thing, so it is worth mentioning alongside Lanturn (is this thing OU?) and Rotom-W.
Singles Calc:
252+ SpA Life Orb Raichu-Alola Surf vs. 252 HP / 0 SpD Marowak-Alola: 273-322 (84.2 - 99.3%) -- guaranteed 2HKO
+2 252+ Atk Marowak-Alola Earthquake vs. 0 HP / 0 Def Raichu-Alola: 598-704 (229.1 - 269.7%) -- guaranteed OHKO
Doubles Calc with Tapu Koko partner:
252+ SpA Life Orb Raichu-Alola Surf vs. 252 HP / 0 SpD Marowak-Alola: 205-242 (63.2 - 74.6%) -- guaranteed 2HKO
252+ Atk Tapu Koko Brave Bird vs. 252 HP / 0 Def Marowak-Alola: 122-144 (37.6 - 44.4%) -- guaranteed 3HKO
+2 252+ Atk Marowak-Alola Earthquake vs. 0 HP / 0 Def Raichu-Alola: 448-528 (171.6 - 202.2%) -- guaranteed OHKO
+2 252+ Atk Marowak-Alola Earthquake vs. 0 HP / 0 Def Tapu Koko: 296-350 (105.3 - 124.5%) -- guaranteed OHKO
On the bright side, Raichu can't OHKO Alolawak on its own regardless of what set it runs, and in doubles it needs its partner-in-crime Tapu Koko to help focus it down with Brave Bird or itemless Acrobatics. If that isn't available or Alolachu doesn't Surf on the switch-in, Alolawak puts both of them in the ground, and this is before thinking about what Alolawak's partner does during the chaos (personally I'd have Celesteela throw up Wide Guard).