Indmar Marine Thermostat 160° Drilled – LT1 & 5.7L Fresh Water Cooled Engines | Part #986034 Maintain optimal engine temperature with this genuine Indmar 160° drilled thermostat, designed specifically for fresh water cooled Indmar marine engines. The precision drilled bypass hole ensures smooth coolant flow and prevents air pockets from forming in the cooling system — a common cause of overheating in tow boats. Compatible with: Indmar LT1 and 5.7L fresh water cooled engines fitted to Malibu, Axis, Moomba, Supra, and Tige boats.