99356A1 Mercruiser Power Steering Cooler | Genuine Used Part

🔧 Product Description

Genuine MerCruiser Power Steering Oil Cooler - Part Number: 99356A1

A genuine MerCruiser power-steering fluid cooler used on selected petrol sterndrive engines.

Mercury 99356A1 is specifically a power-steering cooler. It has an approximately 5-inch cooler body, 1-inch seawater hose connections and push-on steering-fluid hose fittings.

⚙️ Key Features

• Genuine MerCruiser power-steering cooler
• Correct part number 99356A1
• Approximately 5-inch heat-exchanger body
• 1-inch raw-water hose connections
• Push-on power-steering fluid fittings
• Copper-alloy marine heat-exchanger construction

🚤 Compatibility

Documented on

• Various MerCruiser GM 3.0L inline-four engines
• Serial numbers up to approximately 0L340999
• Selected MerCruiser 165HP, 170HP, 180HP and 190HP 3.7L applications with power steering
• Other petrol packages whose cooling diagram specifies 99356A1
• Water Connection: 1 inch
• Fluid Circuit: Power-steering oil
• Fitment Requirement: Confirm hose diameter; use 99356A2 where 1.25-inch water fittings are required

🔌 Function

Raw cooling water flows through the cooler and removes heat from the power-steering fluid passing through the separate internal oil circuit.

⚠️ Common Signs of Failure

• Power-steering fluid overheats or discolours
• Seawater or steering fluid leaks from the cooler
• Internal corrosion allows water and oil circuits to mix
• Cooler body is crushed or blocked
• Hose fittings are corroded or damaged

🔄 Supersession & Cross Reference

OEM Supersession Chain

• 99356A1 original 1-inch connection cooler
• 99356A2 related 1.25-inch water-connection version, not a direct hose-size substitute

OEM / Related Numbers

• 99356A1
• 99356A2 related cooler
• Related raw-water hoses and clamps
• Related power-steering pressure and return hoses

Aftermarket / Verified Equivalents

• Lenco / LE: 99356A1
• Seakamp replacement 99356A1
• Mr Cool / MEC: MRC99356A1
• Marine Energy / Marine Petrol Parts replacement 99356A1
• Custom heat exchanger only when body length, water connection and oil fittings match

📦 Condition

• Genuine used part
• Removed from running engine where applicable
• In good working condition unless otherwise stated
• Pressure-test both circuits before installation