Yamaha 9.9HP 4 Stroke (M17038)

Yamaha 9.9HP Long Tiller 4-Stroke outboard motor is a compact and reliable engine ideal for smaller boats, offering smooth operation, excellent fuel efficiency, and low emissions. Here’s an overview of its features:

General Information

• Brand: Yamaha
• Horsepower: 9.9 HP
• Engine Type: 4-Stroke
• Control Type: Tiller Handle
• Shaft Length: Long (20 inches)
• Fuel Delivery: Carbureted (later models may feature EFI on newer designs).

Key Features

• 4-Stroke Efficiency: Provides quiet operation, improved fuel economy, and reduced emissions compared to 2-stroke engines.
• Tiller Handle Control: Offers precise control with an integrated throttle, gear shift, and tiller grip.
• Long Shaft: Designed for sailboats, deep-V hulls, or applications requiring a 20-inch shaft.
• Manual Start (Optional Electric Start): Dependable pull-start system; some variants may include an electric start option.
• Shallow Water Drive: Allows operation in shallow conditions to protect the propeller and lower unit.
• Lightweight Design: Typically weighing around 85–90 pounds, making it portable and easy to mount.
• Corrosion Resistance: Yamaha’s proprietary coatings ensure durability in both saltwater and freshwater environments.

Performance and Applications

• Top Speed: Capable of powering small boats to speeds of 10–15 mph depending on the load and hull design.

Applications:

•  Dinghies
• Small fishing boats
•  Tender
• Auxiliary motor for sailboats

Maintenance Tips

1. Engine Oil Change

• Change oil every 100 hours or annually.
• Use Yamaha’s recommended 4-stroke marine oil.

2. Spark Plug Maintenance

• Replace plugs every season or every 100 hours. Recommended plug: NGK DR8EA.
• Check the gap (should be 0.7–0.8 mm or 0.028–0.031 inches).

3. Cooling System

• Flush with freshwater after each use, especially in saltwater.
• Replace the water pump impeller every 2–3 years or if overheating occurs.

4. Carburetor Maintenance

• If idling is rough or performance drops, clean or rebuild the carburetor. Use Yamaha’s carburetor cleaner for best results.

5. Gearcase Oil

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

Troubleshooting Common Issues

Engine Won’t Start

Cause: Old fuel, clogged carburetor, or weak spark.

Solution:

• Drain old fuel and clean the carburetor.
• Replace spark plugs and check ignition connections.

Overheating

• Cause: Worn impeller or debris blocking water intake.
• Solution: Replace impeller and clean the intake.

Loss of Power

• Cause: Fouled spark plugs, dirty carburetor, or propeller damage.
• Solution: Clean/replace plugs, clean the carburetor, and inspect the propeller.

Parts and Accessories

OEM Parts

• Yamaha Dealers: Locate genuine parts at authorized Yamaha service centers or dealers.
• Online Retailers: Boats.net and Partzilla.com stock OEM Yamaha parts.

Aftermarket Parts

• Sierra Marine: Offers reliable aftermarket replacements for impellers, spark plugs, and filters.
• Mallory Marine: Known for ignition and fuel system components.

Used Parts

• eBay: Search for “Yamaha 9.9HP 4-stroke parts” for used or reconditioned parts.
• Marine Salvage Yards: Great for finding older or rare components.

Performance Enhancements

Propeller Upgrade:

• Aluminum props are standard, but a stainless steel prop can provide better durability and performance.

Fuel Additives:

• Use stabilizers like Sta-Bil or Yamaha’s fuel conditioner to keep the carburetor clean and prevent ethanol-related issues.

Trim and Tilt Adjustments:

• Adjust the trim angle for optimal speed and fuel efficiency based on the boat’s weight and water conditions.