N.M. Stat. § 66-12-10
The exhaust of every internal combustion engine used on any motorboat shall be effectively muffled by equipment so constructed and used as to muffle the noise of the exhaust in a reasonable manner. This may include but is not limited to such devices as mufflers, exhaust restricters and water-injected exhaust headers. The use of cut-outs or non-muffled headers is prohibited except for motorboats competing in a regatta or boat race approved as provided in Section 66-2-15 NMSA 1978 and for such motorboats while on trial runs during a period not to exceed forty-eight hours immediately preceding the regatta or race and for such motorboats while competing in official trials for speed records during a period not to exceed forty-eight hours immediately following the regatta or race.
NMS § 66-12-10