Yamaha 9.9 / 15 two-stroke (63V) service guide
Oil, gear oil, spark plugs and the service schedule for the Yamaha 9.9 / 15 two-stroke (63V) (9.9 to 15 hp, two-stroke), from the factory service manual, plus how we service it in Hawaiʻi.
Models covered: 9.9 and 15 hp two-strokes: 2 cylinder, 56.0 x 50.0 mm, one carburetor, premix. 9.9C / 15C: 9.9CMH code 682K from S:1009214; 15CMH (15FMH) code 684K from S:1019178. 9.9V / 15V: code 682C: 9.9MH (9.9FMH) S:155562, L:455181, SUL:850196; 9.9EH (9.9FEMH) S:700301, L:600791, SUL:900141; 9.9FEMHR S:630246, L:660183; 9.9ER (9.9FEMR) L:690256. Code 684C: 15MH (15FMH) S:405497, L:153352, SUL:830146; 15EH (15FEMH) S:300231, L:600511, SUL:900131; 15FEMHR S:380261, L:650243.
Quick answers
- What two-stroke oil does a Yamaha 9.9 / 15 two-stroke use?
- 2-stroke outboard motor oil, TC-W3 (NMMA-certified).
- What is the fuel to oil ratio for a Yamaha 9.9 / 15 two-stroke?
- Pre-mixed fuel and oil, 100:1 (9.9C / 15C).
- What gear oil does a Yamaha 9.9 / 15 two-stroke use, and how much?
- GEAR CASE LUBE (USA) or hypoid gear oil, SAE #90. Quantity: 250 cm³ (8.45 US oz, 8.80 Imp oz); fill through the drain hole until it overflows at the level hole.
- What spark plug does a Yamaha 9.9 / 15 two-stroke use?
- NGK B7HS-10 (the 9.9V / 15V also lists BR7HS-10), qty 2. Gap: 0.9 to 1.0 mm (0.035 to 0.039 in).
- How often should a Yamaha 9.9 / 15 two-stroke 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). 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 9.9 / 15 two-stroke?
- The factory schedule says to inspect it at 200 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 9.9 / 15 two-stroke?
- 700 to 800 r/min.
- What is the propeller nut torque on a Yamaha 9.9 / 15 two-stroke?
- 17 N·m (1.7 m·kg, 12 ft·lb).
Maintenance specs
| Two-stroke engine oil | 2-stroke outboard motor oil, TC-W3 (NMMA-certified) |
|---|---|
| Fuel to oil ratio | Pre-mixed fuel and oil, 100:1 (9.9C / 15C). |
| Gear oil | GEAR CASE LUBE (USA) or hypoid gear oil, SAE #90 |
| Gear oil quantity | 250 cm³ (8.45 US oz, 8.80 Imp oz); fill through the drain hole until it overflows at the level hole |
| Gear oil drain plug and oil level plug | Refit the oil level plug first, then the oil drain plug |
| Lower unit holding pressure | 100 kPa (1.0 kg/cm², 14.2 psi) at the oil level hole, must hold 10 seconds; do not over-pressurize |
| Spark plug | NGK B7HS-10 (the 9.9V / 15V also lists BR7HS-10), qty 2 |
| Spark plug gap | 0.9 to 1.0 mm (0.035 to 0.039 in) |
| Spark plug torque (M14) | 25 N·m (2.5 m·kg, 18 ft·lb) |
| Idle speed | 700 to 800 r/min |
| Thermostat | Opens at 48.0 to 52.0 °C (118.4 to 125.6 °F); fully open at 60.0 °C (140 °F); valve lift 3.0 mm (0.12 in) |
| Anode | Inspect: clean scale, oil or grease; replace if worn or excessively consumed. Do not oil, grease or paint it. |
| Propeller nut (M10) | 17 N·m (1.7 m·kg, 12 ft·lb) |
| Power trim and tilt | Not fitted: manual tilt (tilt angles 8, 12, 16, 20 degrees). No trim fluid is listed |
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: 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: spark plugs, fuel filter, anodes
Every 100 hours (6 months)
Replace: gear case oil, gear case plug gaskets, propeller cotter pin
Check: spark plugs, fuel filter, anodes
Every 200 hours (1 year)
Replace: 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 9.9C, 15C service manual LIT-18616-02-59. Specs can change by model year and serial number, so always confirm your exact model from the serial tag on the clamp bracket.