Mariner 25HP Long Tiller – 2S (M13237)

Mariner 25HP Long Tiller – 2-Stroke outboard motor is a lightweight and powerful engine designed for versatility and performance. This model is ideal for fishing boats, utility boats, and recreational use, offering reliability, simplicity, and a high power-to-weight ratio. Here’s a detailed description:

General Information

• Brand: Mariner (produced by Mercury Marine)
• Horsepower: 25 HP
• Engine Type: 2-Stroke
• Control Type: Tiller Handle
• Shaft Length: Long (20 inches)
• Fuel Delivery: Carbureted

Key Features

1. 2-Stroke Power: Offers exceptional acceleration and a high power-to-weight ratio.
2. Lightweight Design: Easy to transport and mount, typically weighing 105–115 pounds.
3. Tiller Handle Control: Simple, responsive steering with an integrated throttle and gearshift.
4. Manual Start (Optional Electric Start): Reliable pull-start system, with some models featuring electric start options.
5. Shallow Water Drive: Enables safe operation in shallow waters, protecting the propeller and lower unit.
6. Durability: Designed for freshwater and saltwater environments with corrosion-resistant coatings.

Fuel and Oil

• Fuel Type: Unleaded gasoline (minimum 87 octane).
• Oil Mix Ratio: 50:1 gasoline-to-oil ratio (use TC-W3 certified 2-stroke marine oil).
• Tank Capacity: External fuel tank, typically 6 gallons.

Performance and Applications

• Top Speed: Capable of pushing small boats to speeds of 20–30 mph, depending on the boat size and load.

Applications:

• Fishing boats
• Utility boats
• Dinghies or tenders

Maintenance Tips

1. Fuel System Maintenance

• Regularly inspect fuel lines, primer bulbs, and connections for wear or leaks.
• Clean or replace the inline fuel filter as needed.
• Use a fuel stabilizer to prevent varnish buildup in the carburetor during storage.

2. Spark Plug Replacement

• Recommended Spark Plug: NGK BUHW or equivalent.
• Replace plugs annually or every 100 hours. Ensure the gap is set to 0.030 inches.

3. Water Pump Impeller Replacement

• Replace every 2–3 years or if water flow is reduced.
• Inspect the cooling system for debris or blockages in the intake screens.

4. Gearcase Oil

• Change lower unit oil annually.
• Look for signs of water intrusion (milky oil) and replace seals if necessary.

5. Carburetor Cleaning

• Clean the carburetor if the engine idles roughly or loses power.
• Rebuild kits are widely available for this model.

Common Issues and Troubleshooting

Starting Problems

• Cause: Clogged carburetor, old fuel, or weak spark.

Solution:

• Drain old fuel, clean or rebuild the carburetor, and replace spark plugs.

Overheating

• Cause: Worn or damaged impeller, debris in the water intake.
• Solution: Replace the impeller and flush the cooling system.

Loss of Power

• Cause: Fouled spark plugs, dirty carburetor, or damaged propeller.
• Solution: Replace plugs, clean the carburetor, and inspect the propeller for damage.

Parts and Accessories

OEM Parts

• Mariner Dealers: Visit authorized Mariner or Mercury Marine dealers for genuine parts.
• Online Retailers:
  • Boats.net
  • MarineEngine.com
  • barosemarineoutboats.uk

Aftermarket Parts

• Sierra Marine: Reliable aftermarket replacement parts, including impellers and filters.
• Mallory Marine: Known for ignition components and carburetor rebuild kits.

Used Parts

• eBay: Search for “Mariner 25HP 2-stroke parts” for used or reconditioned components.
• Marine Salvage Yards: A cost-effective source for rare or discontinued parts.

Performance Enhancements

Propeller Upgrades

• Aluminum props are standard; upgrade to stainless steel for improved durability and performance.
• Select the right pitch based on your boat’s weight and desired performance.

Fuel Efficiency Tips

• Use ethanol-free gasoline to minimize carburetor issues.
• Add a fuel stabilizer like Sta-Bil during storage to prevent fuel breakdown.

Engine Tune-Up

• Regular tune-ups reduce carbon buildup and maintain optimal performance. Mariner 25HP Long Tiller – 2S (M13237)