Mariner 25HP Short Tiller – 2S (M16998)

Mariner 25HP Short Tiller – 2-Stroke (M16998) outboard motor is a reliable, high-performance engine designed for small to medium-sized boats. Known for its durability and efficiency, it is a great choice for fishing, recreational boating, and utility applications. Below is a detailed description of this motor:

Information

• Brand: Mariner
• Horsepower: 25 HP
• Engine Type: 2-Stroke
• Control Type: Tiller Handle
• Shaft Length: Short (15 inches)
• Fuel Delivery: Carbureted

Key Features

• Lightweight and Compact: Weighing around 90–100 pounds, the Mariner 25HP outboard is easy to transport, install, and maneuver on various small boats.
• Tiller Handle Control: The simple tiller handle provides intuitive steering with integrated throttle and gear shift, making it easy to operate.
• Manual Start (Optional Electric Start): Features a reliable pull-start system, with some models offering optional electric start for added convenience.
• Shallow Water Performance: Ideal for shallow water areas such as rivers, lakes, and coastal bays, providing efficient power without damage to the motor.
• Corrosion-Resistant: Built with corrosion-resistant materials, ensuring long-term durability in both saltwater and freshwater environments.

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).
• Fuel Tank: External fuel tank, typically 6 gallons or more, depending on your setup.

Performance and Applications

• Speed Potential: Capable of reaching speeds between 20–25 mph, depending on boat size and load.

Applications:

• Fishing boats
• Small utility boats
• Inflatable boats
• Tenders and dinghies

Maintenance Tips

 Fuel System Maintenance

• Regularly inspect the fuel lines, primer bulb, and connections for wear or leaks.
• Replace the fuel filter at least once a year or when necessary.
• Use a fuel stabilizer, such as Sta-Bil, during long-term storage to prevent carburetor issues.

Spark Plug Replacement

• Recommended Spark Plug: Champion QL77JC4 or equivalent.
• Replace spark plugs every 100 hours or annually, whichever comes first. Be sure to check and set the gap to 0.030 inches.

Water Pump Impeller Maintenance

• Check the impeller every 2–3 years, or sooner if there is a noticeable decrease in water flow or the motor runs hot.
• Flush the cooling system with fresh water after each use in saltwater to prevent corrosion.

Gearcase Oil Change

• Change the lower unit oil at least once a year. Check for signs of water contamination (milky oil) and replace seals if needed.

Carburetor Cleaning

• Clean the carburetor if the engine exhibits rough idling, poor throttle response, or hard starting. Rebuild the carburetor if necessary for optimal performance.

Common Issues and Troubleshooting

Starting Problems

• Cause: Stale fuel, dirty carburetor, or weak spark.
• Solution: Replace old fuel, clean the carburetor, and check the spark plugs and ignition system.

Overheating

• Cause: Worn impeller or debris in the cooling intake.
• Solution: Replace the impeller and clean the water intake screen to restore proper cooling.

Loss of Power

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

Parts and Accessories

OEM Parts

• Mariner Dealers: Genuine parts are available from authorized Mariner dealers.
• Online Retailers:
  • Boats.net
  • MarineEngine.com

Aftermarket Parts

• Sierra Marine: Offers high-quality aftermarket parts such as impellers, fuel filters, and ignition components.
• Mallory Marine: Known for aftermarket carburetor kits, spark plugs, and more.

Used Parts

• eBay: Search for “Mariner 25HP 2-stroke parts” to find used or refurbished components.
• Marine Salvage Yards: An affordable source for hard-to-find parts.

Performance Enhancements

Propeller Upgrade:

• While aluminum props are standard, upgrading to a stainless steel prop can increase durability and improve performance.
• Choose the appropriate prop pitch for your boat’s size and the load you plan to carry.

Fuel Efficiency Tips:

• Use ethanol-free gasoline to reduce carburetor issues and prevent engine knock.
• Add a fuel stabilizer such as Sta-Bil to maintain fuel quality during storage.

Engine Tune-Up:

• Regular decarbonization can help improve engine performance and fuel efficiency by removing carbon buildup. Mariner 25HP Short Tiller – 2S (M16998)