But the Whitecaps took control in the bottom of the seventh when Josh Lester, Daniel Pinero, Will Savage and Cam Gibson all had RBIs to increase the lead to 10-3.
West Michigan added insurance runs in the eighth inning.
Blaise Salter and Lester led the West Michigan offense with three hits apiece while Savage added three RBIs. Lester and Danny Woodrow each had two RBIs.
Starting pitcher Kyle Funkhouser picked up his second win of the year, tossing six innings while allowing four hits and three walks and striking out nine.
The Whitecaps will wrap up their home stand against Fort Wayne at noon on Wednesday when Eudis Idrogo takes the mound.
They are 11-8 on the year, good for second place in the Midwest League’s Eastern Division, a half-game behind first-place Dayton.