Sierra 18-70936 Starboard Cylinder Head Hose - Replaces OMC 340975, 321724, Fits 88-115 HP Outboards

The Sierra 18-70936 is a starboard-side cylinder head hose engineered as a direct replacement for outboard engines that require this specific coolant hose. It routes coolant to and from the starboard cylinder head, and because it is a side-specific part, it is built to the exact length and routing needed for the starboard position only -- it is not interchangeable with the port-side hose. The hose is molded from silicone in white, a material chosen for its resistance to heat cycling, ozone, and the flexing that occurs as the engine runs and cools. Silicone construction helps the hose hold its shape and seal integrity over repeated thermal cycles, reducing the risk of cracking or coolant leaks that can occur with hoses made from lower-grade rubber compounds.

This hose is a direct cross-reference replacement for OMC part numbers 340975 and 321724, making it a straightforward swap for boat owners doing routine cooling-system maintenance or replacing a cracked, hardened, or leaking original hose. It fits a specific range of outboard horsepower and model designations as listed below. Buyers needing the matching port-side cylinder head hose should note that it is a separate part, Sierra 18-70937, since the two sides use different hose lengths and routing and are not interchangeable.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-70936
• Product Type: Cylinder Head Hose
• Side: Starboard
• Material: Silicone
• Color: White
• Weight: 0.41 pounds
• UPC: 808282203375

Fitment

• 90 HP (1994-95)
• 100 HP (1996-97)
• 115 HP (1994-97)
• E88 (1996)
• E90 (1996-98)
• E100 (1996-97)
• E112 (1996)
• E115 (1996-98)
• J88 (1996)
• J90 (1996-98)
• J100 (1997-98)
• J112 (1996)
• J115 (1996-98)

Replaces (OEM)

• 340975
• 321724

Frequently Asked Questions

Is the Sierra 18-70936 for the port or starboard side? The Sierra 18-70936 is the starboard cylinder head hose only. The matching port-side hose is a different part, Sierra 18-70937, so make sure you order the correct side for your engine.

What OEM part numbers does the 18-70936 replace? It replaces OMC 340975 and OMC 321724. If either number is stamped on your old hose, the Sierra 18-70936 is the correct cross-reference for the starboard side.

What outboard models and horsepower does this hose fit? The 18-70936 fits 90 HP (1994-95), 100 HP (1996-97), and 115 HP (1994-97) outboards, as well as the E88 (1996), E90 (1996-98), E100 (1996-97), E112 (1996), E115 (1996-98), J88 (1996), J90 (1996-98), J100 (1997-98), J112 (1996), and J115 (1996-98) model designations.

What material is the 18-70936 cylinder head hose made from? It is made from white silicone, chosen for its resistance to heat and ozone exposure and its ability to keep flexing without cracking through repeated engine heat cycles.

How much does the Sierra 18-70936 weigh? The hose weighs 0.41 pounds.

Can I use the 18-70936 on the port-side cylinder head instead? No. The 18-70936 is molded and routed specifically for the starboard side. For the port side, use Sierra 18-70937, which is a separate part with its own routing and length.

Is this a genuine OEM hose or an aftermarket replacement? The Sierra 18-70936 is an aftermarket replacement hose built as a direct cross-reference for OMC 340975 and 321724, not an OEM-branded part.

Does the 18-70936 come with clamps or fittings? The 18-70936 is the cylinder head hose itself; clamps and fittings are not included as part of this hose.

Why would I need to replace this hose? Cylinder head hoses harden, crack, or develop leaks over time from repeated heat cycling. If your starboard-side coolant hose shows cracking or is leaking, the 18-70936 is the direct replacement.

Does the UPC 808282203375 identify the Sierra 18-70936 hose? Yes, UPC 808282203375 corresponds to the Sierra 18-70936 starboard cylinder head hose.