Yamaha F15 / F20 service guide
Oil, gear oil, spark plugs and the service schedule for the Yamaha F15 / F20 (15 to 20 hp, four-stroke), from the factory service manual, plus how we service it in Hawaiʻi.
Models covered: F15MH, F15EH, F15PH and F20MH, F20EH, F20PH, F20ER, F20PR four-strokes, 2 cylinder 362 cm³, carbureted. Starting serials: F15 model code 6AG from 1000001, F20 model code 6AH from 1000001.
Quick answers
- How much oil does a Yamaha F15 / F20 take?
- 1.6 L (1.69 US qt, 1.41 Imp qt) without filter; 1.8 L (1.90 US qt, 1.58 Imp qt) with filter.
- What engine oil does a Yamaha F15 / F20 use?
- 4-stroke motor oil, API SE, SF, SG, SH, SJ or SL, SAE 5W-30, 10W-30 or 10W-40 (if not available: SAE 15W-40, 20W-40 or 20W-50 with API SH, SJ or SL).
- What gear oil does a Yamaha F15 / F20 use, and how much?
- Hypoid gear oil, API GL-4, SAE 90. Quantity: 300 cm³ (10.14 US oz, 10.58 Imp oz).
- What spark plug does a Yamaha F15 / F20 use?
- NGK DPR6EB-9, qty 2. Gap: 0.8 to 0.9 mm (0.031 to 0.035 in).
- How often should a Yamaha F15 / F20 be serviced?
- The factory schedule lists: Initial 10 hours (1 month); Initial 50 hours (3 months); Every 100 hours (6 months); Every 200 hours (1 year); Every 1,000 hours (5 years). In Hawaiʻi's salt water we do a full yearly service every 200 hours or 1 year, whichever comes first, and a new engine needs its first (break-in) service.
- When should the water pump impeller be replaced on a Yamaha F15 / F20?
- The factory schedule says to inspect it at 200 hours and 1,000 hours. In Hawaiʻi's warm salt water we replace it every 200 hours or 1 year, whichever comes first, because a worn impeller is the most common cause of overheating.
- What is the idle speed of a Yamaha F15 / F20?
- 1,050 ± 50 r/min.
- What is the propeller nut torque on a Yamaha F15 / F20?
- 17 N·m (1.7 kgf·m, 12.5 ft·lb); line up the cotter pin hole by tightening.
Maintenance specs
| Engine oil | 4-stroke motor oil, API SE, SF, SG, SH, SJ or SL, SAE 5W-30, 10W-30 or 10W-40 (if not available: SAE 15W-40, 20W-40 or 20W-50 with API SH, SJ or SL) |
|---|---|
| Engine oil quantity | 1.6 L (1.69 US qt, 1.41 Imp qt) without filter; 1.8 L (1.90 US qt, 1.58 Imp qt) with filter |
| Oil filter | 18 N·m (1.8 kgf·m, 13.3 ft·lb), 64 mm (2.5 in) filter wrench YU-38411; oil the O-ring |
| Engine oil drain bolt (M14) | 27 N·m (2.7 kgf·m, 19.9 ft·lb) |
| Gear oil | Hypoid gear oil, API GL-4, SAE 90 |
| Gear oil quantity | 300 cm³ (10.14 US oz, 10.58 Imp oz) |
| Gear oil drain and check screws | 9 N·m (0.9 kgf·m, 6.6 ft·lb), new gaskets |
| Lower unit holding pressure | 100 kPa (1.0 kgf/cm², 14 psi), must hold at least 10 seconds; do not over pressurize |
| Spark plug | NGK DPR6EB-9, qty 2 |
| Spark plug gap | 0.8 to 0.9 mm (0.031 to 0.035 in) |
| Spark plug torque | 17 N·m (1.7 kgf·m, 12.5 ft·lb) |
| Idle speed | 1,050 ± 50 r/min |
| Thermostat | Begins to open (0.05 mm) at 58 to 62 °C (136 to 144 °F); above 70 °C (158 °F) lift more than 3.0 mm (0.12 in) |
| Anodes | Lower unit anode bolt (M6) 8 N·m (0.8 kgf·m, 5.9 ft·lb); trim tab bolt (M6) 8 N·m (5.9 ft·lb); power tilt model anode bolt (M6) 8 N·m (5.9 ft·lb); power unit anode plug 18 N·m (1.8 kgf·m, 13.3 ft·lb); anode screw (M5) 2 N·m (0.2 kgf·m, 1.5 ft·lb) |
| Propeller nut | 17 N·m (1.7 kgf·m, 12.5 ft·lb); line up the cotter pin hole by tightening |
| Power tilt fluid (PH, PR power tilt models) | ATF Dexron II; fill to overflow at the filler hole, motor tilted up on the tilt stop lever. Reservoir cap 5 N·m (0.5 kgf·m, 3.7 ft·lb), new O-ring |
| Valve clearance, cold | IN 0.15 to 0.25 mm (0.006 to 0.010 in); EX 0.25 to 0.35 mm (0.010 to 0.014 in) |
Service schedule
The factory maintenance intervals, with what is replaced and what is checked at each. Rows marked Hawaiʻi are our shop's yearly service for salt water use.
Initial 10 hours (1 month)
Replace: engine oil, oil drain plug gasket, gear case oil, gear case plug gaskets
Check: spark plugs, fuel filter
Initial 50 hours (3 months)
Replace: gear case plug gaskets, propeller cotter pin
Check: fuel filter, anodes
Every 100 hours (6 months)
Replace: engine oil, oil drain plug gasket, gear case oil, gear case plug gaskets, propeller cotter pin
Check: fuel filter, anodes
Every 200 hours (1 year)
Replace: engine oil, oil filter, oil drain plug gasket, gear case oil, gear case plug gaskets, propeller cotter pin, water pump impeller
Check: spark plugs, fuel filter, thermostat, anodes
Every 1,000 hours (5 years)
Replace: engine oil, oil filter, oil drain plug gasket, gear case oil, gear case plug gaskets, propeller cotter pin, water pump impeller
Check: spark plugs, fuel filter, thermostat, anodes
We replace the water pump impeller at every service from 200 hours up, which can be sooner than the factory schedule, because of Hawaiʻi’s warm salt water.
Source: Yamaha F15 / F20 service manual, LIT-18616-02-96. Specs can change by model year and serial number, so always confirm your exact model from the serial tag on the clamp bracket.