Sierra 18-70936

Keep your outboard engine running smoothly on the water with the Sierra 18-70936 Cylinder Head Hose for the starboard side. This precision-engineered replacement part tackles one of the most critical components in your marine powerplant, ensuring optimal coolant flow to prevent overheating and maintain peak performance during long days on the bay or open sea.

Why Your Engine Needs a Reliable Starboard Cylinder Head Hose

The cylinder head hose plays a vital role in circulating coolant through the starboard cylinder head, dissipating heat from combustion and protecting vital engine components. Over time, exposure to high temperatures, vibration, and corrosive saltwater leads to cracking, bulging, or leaks—common culprits behind rising engine temps and potential catastrophic failure. Upgrading to the Sierra 18-70936 restores factory-level reliability without the premium price tag of OEM parts.

Engineered for Marine Demands

• Durable Construction: Made from high-quality, heat- and chemical-resistant rubber that withstands the harsh marine environment, including saltwater exposure and constant pressure cycles.
• Precise Fit: Direct OEM replacement design ensures seamless integration, eliminating guesswork during installation.
• Reinforced Layers: Multi-ply reinforcement prevents collapse under vacuum or burst under pressure, delivering consistent flow even at wide-open throttle.
• Starboard-Specific Design: Tailored for the unique routing and length requirements on the starboard cylinder head, optimizing space in tight engine compartments.

Perfect Compatibility for Popular Outboards

The Sierra 18-70936 fits a range of Mercury and Mariner inline engines, particularly those in the 3.0L series and select V6 models. Boaters with mid-range outboards from the late '80s through early 2000s often seek this part for routine maintenance or after noticing symptoms like steam from the exhaust or erratic temp gauge readings. Always cross-reference with your engine's serial number for the best match—it's a staple in service manuals for reliable cooling system overhauls.

Effortless Installation Tips from Seasoned Mechanics

Swapping out your old hose is a straightforward DIY job that saves hours at the shop. Here's a pro step-by-step:

1. Drain the coolant and disconnect the battery to stay safe.
2. Loosen clamps on both ends of the hose using a flathead screwdriver or hose clamp pliers—twist gently to avoid damaging fittings.
3. Inspect connected components like the thermostat housing and water pump for wear; replace if needed for a complete refresh.
4. Route the new Sierra hose precisely, securing with stainless steel clamps for corrosion resistance.
5. Refill with marine-grade antifreeze, bleed air from the system, and test-run at idle before hitting full throttle.

Pro Tip: Warm the engine slightly before removal to ease hose separation, and apply a dab of silicone lubricant to new fittings for a snug, leak-free seal.

The Sierra Advantage: Trusted by Boaters Worldwide

Sierra Marine has built a reputation for aftermarket excellence, matching or exceeding OEM specs while prioritizing affordability and availability. This 18-70936 hose isn't just a part—it's peace of mind, backed by rigorous testing for burst pressure, flexibility, and longevity. Skip the downtime and frustration of generic imports; choose Sierra for parts that perform when it counts, from casual cruises to tournament fishing runs.

Spotting Trouble Early: Signs It's Time for Replacement

Don't wait for a breakdown. Watch for soft spots when squeezing the hose, white crusty residue (coolant residue), or a spongy feel under pressure. Regular inspections during annual flushes can extend engine life and catch issues before they sideline your boat.