Indmar Marine Sparks Plug Kit – 5.7L Iridium | Catalyst Exhaust Engine | Part #491009 Upgrade your ignition system with this genuine Indmar iridium spark plug kit, specifically designed for Indmar 5.7L engines fitted with a catalyst exhaust system. Iridium plugs represent the pinnacle of spark plug technology — delivering stronger, more consistent sparks, longer service life, and measurably better performance compared to standard plugs. If you want the best ignition performance from your catalyst-equipped Indmar 5.7L — iridium is the answer. Compatible with: Indmar 5.7L marine engines fitted with catalyst exhaust systems on Malibu, Moomba, Supra, and Tige boats. Contact us to verify fitment for your specific model year