Sierra 18-3603
Sierra 18-3603 — Product description
Keep your outboard motor running cool and efficient with the Sierra 18-3603 water intake hose. Designed as a reliable replacement for worn-out hoses, this durable component ensures steady water flow to your engine's cooling system, preventing overheating during long days on the water. Boaters trust Sierra parts for their precise fit and long-lasting performance, making it an essential upgrade for maintaining peak engine health.
Key Features of the Sierra 18-3603 Water Intake Hose
- Precision Engineering: Molded to exact OEM specifications for seamless integration with popular outboard engines.
- High-Quality Materials: Constructed from reinforced rubber that resists cracking, kinking, and degradation from constant exposure to saltwater, fuel, and high temperatures.
- Optimal Flow Design: Smooth interior walls maximize water circulation, reducing restrictions that could lead to hot spots in the engine block.
- Secure Fittings: Pre-formed ends with barbed connections for a leak-proof seal, eliminating the need for custom trimming.
- Compact and Flexible: Inline configuration fits tight engine compartments without compromising mobility or access.
Engine Compatibility and Fitment
The Sierra 18-3603 is a direct-fit replacement for a range of Mercury and Mariner outboards, particularly 4-cylinder models in the 75 to 125 horsepower range from the late 1980s through the early 2000s. It pairs perfectly with inline powerheads where space is at a premium. Always cross-reference your engine's serial number to confirm compatibility, as variations exist across model years. This hose slots into the lower unit water pickup system, routing fresh water efficiently to the thermostat housing and beyond.
Step-by-Step Installation Guide
- Preparation: Shut off the engine, disconnect the battery, and drain any residual water from the cooling system. Work in a well-ventilated area.
- Removal: Loosen hose clamps on the old intake hose using pliers or a screwdriver. Gently twist and pull the hose free from the fittings, noting its orientation for reinstallation.
- Inspection: Clean the mating surfaces on the lower unit and thermostat housing to remove corrosion or debris that could cause leaks.
- Installation: Slide the new Sierra 18-3603 hose onto the barbs, ensuring full seating. Position clamps over the ridges and tighten securely without over-crimping.
- Testing: Reconnect the battery, start the engine on muffs or in the water, and check for leaks. Monitor the temperature gauge during a test run.
Pro tip: Apply a thin layer of marine grease to the barbs for easier installation and removal in the future.
Benefits and Maintenance Tips
Replacing a faulty water intake hose like the Sierra 18-3603 can extend your engine's life by years, avoiding costly repairs from overheating damage. It restores factory-level cooling efficiency, which translates to better fuel economy and smoother operation under load. Regular inspections are key—check hoses annually or every 100 hours of use for signs of brittleness, swelling, or white powdery residue from electrolysis.
Pair this hose with a full cooling system flush using a vinegar solution to dissolve salt buildup, ensuring optimal performance season after season. Boaters report fewer impeller failures and alarm triggers after proactive hose swaps.
Frequently Asked Questions
What engines is the Sierra 18-3603 water intake hose compatible with?
It fits Mercury and Mariner 4-cylinder outboards from 75-125 HP, typically late 1980s to early 2000s models. Verify with your engine serial number.
How do I know if my water intake hose needs replacement?
Look for cracks, soft spots, leaks, or restricted water flow indicated by high engine temps or weak tell-tale stream.
Can I install the Sierra 18-3603 myself?
Yes, it's a straightforward DIY job taking 15-30 minutes with basic tools like pliers and screwdrivers.
What material is the Sierra 18-3603 hose made from?
Reinforced marine-grade rubber designed for resistance to heat, ozone, and saltwater exposure.
Will this hose improve my engine's cooling performance?
Absolutely, by ensuring unrestricted water flow, it helps maintain optimal temperatures and prevents overheating.
How often should I replace the water intake hose?
Inspect yearly; replace every 3-5 years or at signs of wear, regardless of hours run.
Does the Sierra 18-3603 come with clamps?
Clamps are not included; reuse existing ones if in good condition or purchase stainless steel worm-gear style.
SKU: NVN-4003889
MPN: 18-3603
UPC: 808282124731
Technical specifications
| Brand | Sierra Engine Parts |
| Model | Sierra 18-3603 |
| SKU / MFR# | 4003889 |
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