Thermostat housing to exhaust manifold. 1 in. (25 mm) I.D.. A reliable cooling system is key to keeping any marine engine performing at its best, and the Mercury MerCruiser Molded Hose (32-861634) plays a crucial role in that equation. Designed for 3.0L MerCruiser engines, this hose provides a secure, leak-free connection between the thermostat housing and exhaust manifold, ensuring steady coolant flow and optimal temperature regulation. Over time, heat, pressure, and exposure to harsh marine conditions can wear down hoses, leading to cracks, leaks, or reduced efficiency-making timely replacement essential.. Why This Hose Matters:. Keeps the Cooling System Running Smoothly - Maintains a consistent flow of coolant, helping to prevent overheating and extend engine life.. OEM Fit & Durability - Built to Mercury's exact specifications for a precise, hassle-free installation on 3.0L MerCruiser engines.. Marine-Grade Construction - Designed to withstand high temperatures, pressure changes, a