Sierra 18-3551 Mercruiser Thermostat
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Sierra 18-3551 Mercruiser Thermostat Product Description
Keeping your Mercruiser engine running at peak performance starts with reliable temperature regulation. The Sierra thermostat steps in as a precision-engineered replacement that maintains optimal coolant flow, preventing overheating during those long days on the water. Designed for durability in harsh marine environments, it ensures your engine stays cool under load without compromising efficiency.
Boat owners know the frustration of erratic engine temps—sudden spikes that cut runs short or sluggish warm-ups that waste fuel. This thermostat addresses those pain points head-on, using high-quality materials that resist corrosion and wear from saltwater exposure and constant vibration.
Standout Features and Real-World Benefits
- Exact-Fit Design: Matches original specifications for seamless integration, eliminating guesswork during swaps.
- Robust Construction: Brass body and premium wax pellet for consistent operation across thousands of cycles.
- Quick Response: Opens precisely at the right temperature to balance cooling and performance, reducing wear on pumps and hoses.
- Corrosion Resistance: Engineered to handle freshwater, saltwater, and antifreeze mixes without degrading.
- Cost-Effective Reliability: Delivers OEM-level performance at a fraction of the cost, ideal for frequent maintenance or high-hour engines.
Unlike stock parts that might stick or flutter, this unit provides stable operation, helping extend the life of gaskets, impellers, and manifolds. Boaters report smoother idling and better fuel economy after installation, especially on V8 setups pounding through choppy conditions.
Perfect Fit for Popular Mercruiser Models
Engineered as a direct replacement for a range of GM-based Mercruiser powerplants, it slots right into inline and V configurations. Think 4-cylinder workhorses up to beefy 350 CID blocks—always cross-check your service manual for the ultimate match, as housing variations exist across years.
Pro tip: Pair it with a fresh gasket kit for leak-free results. It's a staple for Alpha/Bravo sterndrives where heat management is critical for sterndrive longevity.
Step-by-Step Installation Insights
- Prep Work: Drain coolant, remove upper/lower hoses, and note the orientation of the old unit.
- Removal: Loosen housing bolts carefully—watch for brittle gaskets that might crumble.
- Install New: Apply sealant to the new gasket, seat the thermostat (jiggle valve up), and torque to spec (usually 10-15 ft-lbs).
- Refill and Test: Burp the system thoroughly, run the engine to operating temp, and monitor with an infrared thermometer for peace of mind.
- Final Check: Inspect for leaks after a few heat cycles; adjust belts if needed for impeller bite.
Most swaps take under an hour with basic tools. If you're chasing persistent overheat codes, inspect the full cooling circuit—radiator cap, raw water pump, and exhaust risers often share blame.
Maintenance Essentials and Common Fixes
Thermostats don't last forever; inspect annually or every 100 hours. Signs of trouble include slow warm-up (stuck open), overheating at WOT (stuck closed), or temp gauge swings. Test off-engine by heating in a pot— it should pop open around standard operating range.
"Swapped mine on a 5.7L Mercruiser after noticing inconsistent temps during trolling. Engine runs like new now—no more nursing it home." – Experienced boater feedback.
Extend service intervals by flushing with a descaler yearly. Avoid mixing coolant types, as it accelerates wax pellet failure.
Frequently Asked Questions
What temperature does the Sierra Mercruiser thermostat open at?
It reliably opens at the standard operating temperature suited for most Mercruiser engines, ensuring quick warm-up and efficient cooling under load.
Is this thermostat compatible with both carbureted and EFI Mercruiser engines?
Yes, its universal design fits a broad range of carbureted and fuel-injected GM blocks used in Mercruiser applications.
How do I know if my current thermostat is failing?
Look for symptoms like engine overheating at high RPMs, slow warm-up times, erratic temperature gauge readings, or coolant flow issues.
Do I need to replace the gasket when installing a new thermostat?
Absolutely—always use a new gasket to prevent leaks and ensure proper sealing under pressure.
Can this thermostat be used in saltwater environments?
Yes, its corrosion-resistant materials make it ideal for both freshwater and saltwater boating, holding up to constant exposure.
What's the expected lifespan of this replacement thermostat?
With proper maintenance, it typically lasts 2-5 years or 300-500 hours, depending on usage and cooling system care.
Should the thermostat be installed with the jiggle valve facing up?
Correct orientation is key—position the jiggle valve (or bleed hole) upward to allow air pockets to escape during operation.
Save $2 when you buy the Sierra 18-3551 Mercruiser Thermostat for only $15 from NVN Marine! Same day shipping before 3pm.
Sierra 18-3551 Mercruiser Thermostat Technical Specifications
| Type: | |
|---|---|
| Vendor: |
Sierra Engine Parts |
| Weight: |
0.13 lb |
| Temp.: |
142° |
| Replaces: |
Mercury 59137, 807252T1 Chrysler 4142885 Crusader 96319 Pleasurecraft R026002E |
Sierra 18-3551 Mercruiser Thermostat User Reviews
Sierra 18-3551 Mercruiser Thermostat Shipping & Return
| Shipping Weight: |
0.13 lb |
|---|---|
| Box Sizes: |
2.00 (h) x 6.00 (w) x 7.00 (l) |
| Cubic Feet: |
84.0 |
| Returnable: |
Yes |
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