Sierra 18-70955 Molded Hose, Oil Cooler to Thermostat Housing for MC175/205 & 4.3L MerCruiser

The Sierra 18-70955 is a molded cooling system hose engineered to connect the oil cooler to the thermostat housing on applicable MerCruiser engines. It is designed for thermostat housings that have all four hose connectors cast directly into the housing itself, with no separate "T" connector required. In this configuration, two hoses run to the manifold and two hoses run to the elbow, and the 18-70955 is molded to complete that oil cooler to thermostat housing connection with a precise, correct-fit bend rather than a straight length that has to be forced into shape.

Sierra molds this hose for fresh water or raw water cooling systems, shaping it to maintain full, unrestricted water flow through the bend while also simplifying installation compared to a generic straight hose. Construction uses EPDM tubing with a synthetic knit reinforcement, giving the hose the flexibility and heat resistance needed for engine bay cooling circuits. It is finished in white and built to OEM quality standards, so fit, form, and function match the original equipment it replaces. This hose is intended for the specific MerCruiser engines and model years listed below; confirm your engine designation before ordering.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-70955
• Product Type: Molded Hose
• Function: Oil cooler to thermostat housing connection
• Thermostat Housing Configuration: All four hose connectors cast into the housing (no "T" connector)
• Hose Routing: Two hoses to manifold and two hoses to elbow
• Material: EPDM tubing with synthetic knit reinforcement
• Color: White
• Weight: 0.37 pounds

Fitment

• MC175/205 (1987)
• 4.3L (1988-92)
• 4.3L (Gen II) (1992-95)
• 4.3LX (Gen II) (1992-95)

Frequently Asked Questions

What does the Sierra 18-70955 hose connect? The 18-70955 is a molded hose that connects the oil cooler to the thermostat housing, on housings where all four hose connectors are cast into the housing itself with no separate T connector.

Which engines is the 18-70955 designed for? This hose fits the MC175/205 (1987), 4.3L (1988-92), 4.3L (Gen II) (1992-95), and 4.3LX (Gen II) (1992-95) MerCruiser engines.

Is this hose a straight length I have to bend myself? No, the Sierra 18-70955 is molded into the correct shape for the oil cooler to thermostat housing routing, so it fits the bend without being forced into place like a generic straight hose.

What material is the 18-70955 hose made from? It is built from EPDM tubing with a synthetic knit reinforcement, a construction suited to the heat and flexing found in a marine engine cooling circuit.

What color is the Sierra 18-70955? The hose is white.

How much does the 18-70955 hose weigh? It weighs 0.37 pounds.

How many hoses come with the 18-70955, and how do they route? The 18-70955 is used in a configuration with two hoses to the manifold and two hoses to the elbow, connecting the oil cooler to the thermostat housing.

Is the 18-70955 compatible with a thermostat housing that uses a separate T connector? No, this molded hose is designed for thermostat housings with all four hose connectors cast into the housing itself, not housings that use a separate T connector.

Does the 18-70955 work for both fresh water and raw water cooling systems? Yes, Sierra molds this hose for use in either fresh water or raw water cooling systems on the applicable MerCruiser engines.

Is the Sierra 18-70955 built to OEM quality? Yes, Sierra designs the 18-70955 to OEM quality standards so it matches the original hose in fit, form, and function.

Will the 18-70955 fit a 5.0L or 5.7L MerCruiser engine? No, the 18-70955 is fitted to the MC175/205, 4.3L, and 4.3LX engines listed; other MerCruiser V8 engines use a different Sierra part number.