Introduction

Regular 100-hour maintenance of your Yamaha F115 outboard engine is the key to reliable performance, fuel efficiency, and longer engine life. In this guide, we’ll walk through spark plug inspection, oil and oil filter replacement, fuel-water separator servicing, inline fuel filter changes, and essential lubrication points. By following Yamaha’s specifications and using genuine NGK and Yamalube products, you’ll prevent costly breakdowns and keep your boat running smoothly. Ready for professional support? Don’t forget to request your personalized service quote at the end of this article.

1. Spark Plug Inspection & Replacement

Performing a spark plug check first reveals any serious engine issues before you invest time in oil changes or filter swaps.

1. Remove & Inspect

   • Detach spark plug caps and loosen plugs with a socket wrench (“lefty loosey, righty tighty”). Look for carbon build-up, rounded electrodes, deposits, or white porcelain indicating overheating.

2. Select NGK Plugs

   • Use factory-recommended pre-gapped NGK plugs (e.g., LFR6A-11 or LKR6E; resistor “R” type if specified) to ensure proper gap and minimize RFI.

3. Reinstall to Spec

   • Torque plugs to 18 ft-lb (cast iron) or up to 21.6 ft-lb (aluminum) and reattach wires in the correct order—listen for the click.

2. Oil & Oil Filter Change

Changing oil and filter removes contaminants and maintains lubrication integrity.

1. Extract Old Oil

   • Warm engine; use a vacuum pump via dipstick port to remove oil, or drain with a pan—about 3.9 qt capacity.

2. Replace Filter

   • Remove old filter, coat new filter seal with fresh oil, hand-tighten only.

3. Refill

   • Add 10W-30 Yamalube oil (or 20W-40 in extreme climates), check level with dipstick.

3. Fuel-Water Separator Service

Moisture in ethanol fuels causes corrosion—regularly replace your separator.

1. Remove Old Unit

   • Unseat with wrench; catch drips.

2. Lubricate Seal

   • Lightly grease O-ring; hand-tighten new separator only.

4. Inline Fuel Filter Replacement

Protect injectors and pumps by replacing primary and secondary filters.

• Primary 10-micron filter between tank and engine.

• Lift pump outlet mesh filter and VST inlet filter per schedule.

5. Lubrication & Additives

Protect and condition your engine during service.

• Yamalube Ring-Free additive at each fill-up to prevent gum and carbon build-up.

• T-9 Spray on powerhead, electricals, and trim/tilt to repel saltwater corrosion.

• Marine grease on throttle/shift cables, pivot tubes, and three zerks (crank-to-driveshaft, steering tube fittings).

Ensure your Yamaha F115 receives expert care from certified technicians using genuine parts. Submit the form today and “Keep Them Boating!”