Murray 21P550HW Lawn Mower Manual
The Murray 21P550HW is a 21-inch push lawn mower featuring a 550cc Briggs & Stratton engine, 3-in-1 cutting system (mulch/bag/side discharge), 6-position single-lever height adjustment, durable steel deck, easy-start system, and large rear wheels for enhanced maneuverability. This manual covers safety instructions, assembly, operation, maintenance, troubleshooting, and storage guidelines to ensure optimal performance and longevity of your mower.
Safety Instructions
Always read and follow all safety rules before operating your Murray lawn mower.
| Hazard | Precaution |
|---|
| Fuel Handling | Refuel outdoors only when engine is cool. Use approved container. |
| Blade Contact | Keep hands and feet away from cutting deck. Disconnect spark plug before servicing. |
| Debris Projection | Clear mowing area of stones, toys, and other objects. Wear eye protection. |
| Slope Operation | Mow across slopes, not up and down. Use extra caution on inclines. |
| Children & Pets | Keep bystanders, especially children and pets, at a safe distance. |
| Hot Surfaces | Avoid contact with muffler and engine; they become extremely hot during use. |
| Starting Procedure | Start engine outdoors only. Never in an enclosed area. |
| Electrical Hazards | Do not operate mower in wet grass or during rain. |
| Clothing | Wear substantial footwear, long pants, and close-fitting clothing. |
| Unattended Operation | Never leave mower running unattended. |
Assembly Guide
Unpack all parts and inspect for damage. Assembly requires basic tools (included).
- Handle Assembly: Attach upper and lower handle sections using provided bolts and wing nuts. Ensure handle is secure and upright.
- Wheel Installation: Slide wheels onto axles and secure with push nuts or washers and cotter pins as per model.
- Height Adjustment Lever: Connect the linkage rod to the lever and cutting deck as shown in the diagram.
- Bagging/Mulching Kit: Attach rear bagger or mulch plug according to your desired cutting mode.
- Oil & Fuel: Add engine oil (SAE 30) to the full mark on the dipstick. Fill fuel tank with fresh, unleaded gasoline.
WARNING! Do not attempt to start the engine until assembly is complete and all parts are properly tightened.
Controls & Features
Familiarize yourself with the location and function of all controls.
Primary Controls:
- Engine Control Lever: Must be held in position to start and run the engine.
- Recoil Starter Handle: Pull to start the engine.
- Drive Control Lever (if equipped): Engages self-propelled drive system.
- Height Adjustment Lever: Single lever adjusts all four wheels to 6 cutting positions (1.25" - 3.75").
- Fuel Shut-Off Valve: Located near the fuel tank.
- Primer Bulb: Press 3 times for cold starts.
- Choke Control: Use for cold starting.
Specifications
- Model: Murray 21P550HW
- Cutting Width: 21 inches
- Engine: Briggs & Stratton 550cc, 140cc OHV
- Cutting System: 3-in-1 (Mulch, Bag, Side Discharge)
- Cutting Height: 6 positions, 1.25" - 3.75"
- Deck Material: Powder-coated steel
- Wheels: 8" rear, 7" front
- Start Type: Recoil
- Fuel Tank Capacity: 1.0 quart (0.95 L)
- Oil Capacity: 20 oz (0.6 L) SAE 30
- Weight: Approx. 65 lbs (29.5 kg)
Operation Instructions
Follow these steps for safe and effective mowing.
- Pre-Start Check: Check oil level, fuel level, and ensure cutting deck is clear of debris.
- Starting the Engine:
- Move the mower to a clear, flat area.
- Push the primer bulb 3 times (cold engine).
- Set the choke to the "ON" position.
- Hold the engine control lever against the handle.
- Pull the recoil starter handle briskly.
- Once engine starts, move choke to "OFF".
- Mowing: Walk at a steady pace, overlapping each pass slightly. Avoid mowing in wet grass.
- Stopping: Release the engine control lever. The engine and blade will stop.
- Emptying Bag: Stop engine completely before removing or emptying the grass bag.
Tip: For the best cut, mow when grass is dry and keep the blade sharp.
Cutting System Setup
Configure your mower for mulching, bagging, or side discharge.
- Mulching: Install the mulch plug to close the rear discharge opening. Grass clippings are finely cut and returned to the lawn.
- Bagging: Attach the grass bag to the rear deck hooks. Ensure the bag is securely fastened.
- Side Discharge: Remove the mulch plug and do not attach the bag. Clippings are discharged from the side chute (deflector must be installed).
CAUTION! Always ensure the appropriate chute or plug is securely installed before operation. Never operate without the discharge deflector in place for side discharge mode.
Maintenance Schedule
Regular maintenance ensures safety, performance, and extends mower life.
| Task | Frequency | Procedure |
|---|
| Check Engine Oil Level | Before each use | Use dipstick; add SAE 30 oil if low. |
| Check/Sharpen Blade | Every 25 hours or as needed | Disconnect spark plug. Remove blade, sharpen balance, re-tighten securely. |
| Clean Underside of Deck | After each use | Tip mower on its side (carburetor side up) and scrape clean. |
| Air Filter Inspection | Every 25 hours | Clean foam pre-filter. Replace paper filter if dirty. |
| Check Wheel & Drive Bolts | Every 10 hours | Tighten any loose hardware. |
| Replace Spark Plug | Every 100 hours or season | Gap to 0.030". Use Champion RC12YC or equivalent. |
Engine Care
Proper engine maintenance is critical for reliable starting and operation.
- Oil Change: Change oil after first 5 hours of operation, then every 50 hours or seasonally. Drain when warm.
- Air Filter: Service foam pre-cleaner in warm soapy water every 25 hours. Replace paper cartridge annually.
- Fuel System: Use fresh, unleaded gasoline (87 octane minimum). Add fuel stabilizer for storage over 30 days.
- Spark Plug: Clean and re-gap periodically. Replace annually for best performance.
- Cooling Fins: Keep engine cooling fins and air intake areas clear of grass clippings and debris.
WARNING! Always disconnect the spark plug wire before performing any maintenance.
Storage Guidelines
Prepare your mower for seasonal storage to prevent damage.
- Fuel System:
- Option A: Run the engine until it stops to use up all fuel in the carburetor and tank.
- Option B: Add a fuel stabilizer to a full tank, run engine for 5 minutes, then shut off fuel valve and run until it stops.
- Clean Thoroughly: Clean the mower deck, wheels, and engine of all grass, dirt, and debris.
- Change Oil: Change the engine oil (see Engine Care).
- Remove Spark Plug: Add one tablespoon of oil into the cylinder, pull starter cord slowly to distribute, then reinstall plug.
- Battery (if equipped): Remove and store in a cool, dry place. Charge periodically.
- Storage Location: Store in a clean, dry place, protected from the elements. Cover the mower.
Warranty Information
Murray mowers are backed by a limited warranty. Please retain your proof of purchase.
- Residential Use: 2-year limited warranty on the mower. Engine warranty is provided by Briggs & Stratton (typically 2 years).
- What is Covered: Defects in material or workmanship under normal use and maintenance.
- What is Not Covered: Damage from misuse, neglect, accident, improper maintenance, or commercial use.
- Service: For warranty claims or service, contact an authorized Murray service center. Do not return to the retailer.
- Contact: For customer support, call 1-800-XXX-XXXX or visit www.murray.com.
Copyright © Murray LLC. Murray is a trademark of Briggs & Stratton Power Products Group, LLC.
Troubleshooting
| Symptom | Possible Cause | Corrective Action |
|---|
| Engine will not start | Empty fuel tank, old fuel, clogged air filter, spark plug wire disconnected, choke/primer not used correctly. | Add fresh fuel, clean/replace air filter, check spark plug connection, use choke/primer for cold starts. |
| Engine runs poorly or stalls | Dirty air filter, old fuel, water in fuel, clogged fuel line, dirty spark plug. | Clean air filter, drain and replace fuel, check fuel line, clean/replace spark plug. |
| Excessive vibration | Damaged or unbalanced blade, loose blade bolt, debris stuck in blade. | Stop engine, disconnect spark plug. Inspect blade for damage/balance, tighten bolt, remove debris. |
| Uneven cutting height | Uneven tire pressure, worn/deformed wheels, cutting deck not level. | Check tire pressure, inspect wheels for damage, level the cutting deck per manual. |
| Mower does not self-propel (if equipped) | Drive belt loose or broken, drive control cable out of adjustment. | Inspect drive belt for wear and tension. Adjust drive control cable. |
| Grass bag does not fill | Deck clogged, grass too wet/dense, improper cutting height. | Clean underside of deck, mow when grass is dry, raise cutting height. |
For Technical Support: 1-800-XXX-XXXX | www.murray.com
Murray 21P550HW Lawn Mower Manual © - All Rights Reserved 2025