Exhibit 99 MAYVILLE ENGINEERING COMPANY ANNOUNCES FOURTH QUARTER AND FULL-YEAR 2023 RESULTS MILWAUKEE, Wis., March 5, 2024 – Mayville Engineering Company (NYSE: MEC) (the “Company” or “MEC”), a leading value-added provider of design, prototyping and manufacturing solutions serving diverse end markets, today announced results for the three and twelve-months ended December 31, 2023. FOURTH QUARTER 2023 RESULTS (All comparisons versus the prior-year period) ● Net sales of $148.6 million, or +15.6% y/y, includi ...