The Canucks (2-5), who lost to the Anaheim Ducks on Wednesday night, again choose to keep many of their stars off the ice. Mikael Samuelsson and Manny Malhotra were the only Canucks to play who recorded double figures in goals last season.
Both teams will play their final preseason game on Saturday, with the Sharks visiting Phoenix and the Canucks, who have lost four straight, hosting Edmonton.
Vancouver goalie Cory Schneider recorded 33 saves. The Canucks have been outscored 23-13 thus far in the preseason.
Thornton recovered a Patrick Marleau rebound and found Pavelski for the power-play goal, a clear shot into the upper left corner that gave the Sharks a 1-0 lead with 9:29 remaining to play in the second period.
Thornton again picked up a missed Marleau shot early in the third period and found Boyle in front of the net for a wrist shot into the upper right corner.
McGinn added his goal late in the third period. Clowe carried the puck down the ice and gave McGinn a nice feed for a backhand goal.
The Sharks, looking to improve their penalty kill, stopped five power-play opportunities, twice on a two-man advantage. San Jose has killed off 22 of 24 power plays this preseason.