EXHIBIT 23 CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM We hereby consent to the incorporation by reference in the Registration Statement No. 333-75521 on Form S-8 of Mercantile Bank of West Michigan of our report dated May 6, 2004, which is included in this Annual Report on Form 11-K of Mercantile Bank of West Michigan 401(k) Plan for the year ended December 31, 2003. /s/ Crowe Chizek and Company LLC -------------------------------- Crowe Chizek and Company LLC Grand Rapids, Michigan June 21, 2004