Former Namibian international David Philander, playing on the left wing, also opened his tryscoring account with a 70m effort after an intercept six minutes from time to seal the win.
West Coast started with a hiss and a roar, dominating possession and territory for the first 15 minutes during which time they score a good try to second five-eighths Sean McClure, after forwards and backs combined.
But from the moment Yortt scored a converted try in the 17th minute, it was all Poverty Bay. They took the game to a Coast side who did not help themselves with weak tackling as the home side built up a 21-8 halftime lead.
Although on the losing side, Coast No 8 Rowan O'Gorman was outstanding and was easily his side's best player.
Poverty Bay 31 (Adam Ross 2, Henry Yortt, Jason Tuapawa, David Philander tries; Scott Leighton 3 cons) West Coast 13 (Sean McClure, Troy Tauwhare tries; Corey Deans pen). HT: 21-8.