Mercury MerCruiser Quicksilver Cooling Hose — 32-864551

Mercury MerCruiser Quicksilver Molded Cooling Hose — 32-864551

This genuine OEM molded cooling hose from Mercury Marine connects the intake manifold bypass to the water circulating pump on select MerCruiser gasoline engines with a closed-cooling system. Formed to the exact curvature of the factory routing, it installs without trimming or modification and restores proper coolant flow through the bypass circuit.

The intake bypass hose plays a key role in regulating coolant temperature during warm-up and steady-state operation. A cracked or deteriorated hose at this position can reduce system efficiency and lead to overheating. Using the correct OEM part ensures the right bend geometry, wall thickness, and material compatibility for your engine’s cooling demands.

Product Details

• Part Number: 864551 (full reference: 32-864551)
• Brand: Mercury Quicksilver
• Type: Molded engine cooling hose
• System: Closed cooling — intake manifold bypass to water circulating pump
• Condition: New, genuine OEM
• GTIN / UPC: 745061554535

Compatible Applications

• MerCruiser 4.3L MPI Alpha / Bravo (select serial ranges)
• MerCruiser 5.0L MPI Alpha / Bravo (select serial ranges)
• MerCruiser 350 MAG MPI Alpha / Bravo (select serial ranges)
• Other MerCruiser gasoline engines using the same closed-cooling layout
• Confirm fitment using your engine serial number and closed-cooling system diagram before ordering

Serial Number Fitment Notice

MerCruiser uses different molded hoses depending on engine family, raw-water versus closed cooling, riser arrangement, and production serial range. Always verify your engine model, serial number, and cooling configuration against the parts diagram before ordering to confirm 32-864551 is correct for your application.

When to Replace

• Hose is cracked, hardened, swollen, or chafed
• Leaking or seeping at either molded end or clamp contact point
• Visible deterioration or deformation from heat cycling
• Coolant loss or overheating traced to the bypass circuit

Installation Notes

• Allow the engine to cool completely before beginning service
• Note the original hose routing and clamp positions before removal
• Inspect the intake manifold bypass fitting and circulating pump connection for corrosion or damage
• Secure firmly at both connections per Mercury installation guidelines
• Replace clamps if worn or corroded
• Verify the system is leak-free at operating temperature after installation

Related Parts

• Mercury MerCruiser Quicksilver Cooling Hose — 32-864552 (Thermostat Housing to Upper Manifold)
• Mercury MerCruiser Quicksilver Cooling Hose 864578 — Drain Fitting to Check Valve
• Mercury MerCruiser 864579 Cooling Hose — Check Valve to Thermostat Housing
• Mercury Cooling Hose — 160211
• Mercury MerCruiser 3.0L Drain System Adapter Assembly — 22-862605T1
• #3 SS Mini Hose Clamp 5/16"–9/16"
• Mercury MerCruiser Nylon Hose Clamp — 54-415825

Parts Desk Insights

Best use: Order 32-864551 when your closed-cooling system diagram shows the intake manifold bypass to water circulating pump connection — that’s the precise identifier that separates it from nearby hoses like 864552, 864539, and 864431, which connect different components in the same system. The most common issue is customers ordering by engine family alone without checking the cooling configuration; this hose only applies to closed-cooling setups, not raw-water cooled engines. If you’re servicing the cooling system, consider replacing sibling hoses at the same time — they share the same service life. Have your engine serial number ready and our parts desk can confirm which hoses in this group apply to your engine.