# 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

## Details

- **Price:** 100.0 AUD
- **Vendor:** Sawley's Auto and Marine
- **Type:** Cooling System
- **Tags:** Sawley’s AAM Used Parts – Oil Pumps & Components | Engine Lubrication Systems

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 100.00 AUD | In stock |

## Images

- 99356A1 Mercruiser Power Steering Cooler | Genuine Used Part
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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/99356a1-mercruiser-oil-cooler-genuine-used-part)
> Updated: 2026-09-06