Yamaha 40 / 50 two-stroke (63B) service guide
Oil, gear oil, spark plugs and the service schedule for the Yamaha 40 / 50 two-stroke (63B) (40 to 50 hp, two-stroke), from the factory service manual, plus how we service it in Hawaiʻi.
Models covered: 40 and 50 hp two-strokes: 3 cylinder, 698 cm³ (42.6 cu in), 67.0 x 66.0 mm, three carburetors. Approved model code 6H4 for the 40 hp and 6H5 for the 50 hp. LIT-18616-02-65: 40TR from L:1005165, 50TR from L:1004305, both oil injected. LIT-18616-01-81, USA / Canada name: C40MH (40VMH) S:010262, L:310801; 40MH (40VMHO) S:191877, L:491566; C40ER (40VE) S:060285, L:360173; 40ER (40VEO) S:110760, L:842362, X:740146; P40TH (40VEHTO) L:430386; C40TR (40VET) L:921505; 40TR (40VETO) S:880367, L:544974, X:900196; 50ER (50HEDO) S:090431, L:521079; C50TR (50HET) L:900101; 50TR (50HETO) S:210142, L:444058, X:750216; oil injection (1.5 L tank) on 40MH, 40ER, P40TH, 40TR, 50ER, 50TR and worldwide 40VMO, 50HMHO, 50HMO, 50HMDO.
Quick answers
- What two-stroke oil does a Yamaha 40 / 50 two-stroke use?
- 2-stroke outboard motor oil (TC-W3 in LIT-18616-01-81). Oil injected models: oil tank 1.5 L (1.6 US qt, 1.3 Imp qt).
- What is the fuel to oil ratio for a Yamaha 40 / 50 two-stroke?
- Premix models (C40MH, C40ER, C40TR, C50TR): 50:1. Oil injected models (40MH, 40ER, P40TH, 40TR, 50ER, 50TR): no mixing ratio, oil is fed by the injection pump.
- What gear oil does a Yamaha 40 / 50 two-stroke use, and how much?
- GEAR CASE LUBE (USA) or hypoid gear oil, SAE #90. Quantity: 40 hp and 50 hp alike: 430 cm³ (14.5 US oz, 15.1 Imp oz); fill through the drain hole until it overflows at the level hole.
- What spark plug does a Yamaha 40 / 50 two-stroke use?
- 40 hp: NGK B7HS-10; 50 hp: NGK B8HS-10 (for Canada and Europe LIT-18616-01-81 lists BR7HS-10 and BR8HS-10); qty 3. Gap: 0.9 to 1.0 mm (0.035 to 0.039 in).
- How often should a Yamaha 40 / 50 two-stroke be serviced?
- The factory schedule lists: Initial 10 hours (break-in); 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 40 / 50 two-stroke?
- The factory schedule gives no replacement interval. 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 40 / 50 two-stroke?
- 800 ± 50 rpm.
- What is the propeller nut torque on a Yamaha 40 / 50 two-stroke?
- 35 N·m (3.5 m·kg, 25 ft·lb) in LIT-18616-02-65; If the nut does not line up with the cotter pin hole, turn it in further.
Maintenance specs
| Two-stroke engine oil | 2-stroke outboard motor oil (TC-W3 in LIT-18616-01-81). Oil injected models: oil tank 1.5 L (1.6 US qt, 1.3 Imp qt) |
|---|---|
| Fuel to oil ratio | Premix models (C40MH, C40ER, C40TR, C50TR): 50:1. Oil injected models (40MH, 40ER, P40TH, 40TR, 50ER, 50TR): no mixing ratio, oil is fed by the injection pump. |
| Gear oil | GEAR CASE LUBE (USA) or hypoid gear oil, SAE #90 |
| Gear oil quantity | 40 hp and 50 hp alike: 430 cm³ (14.5 US oz, 15.1 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 | 40 hp: NGK B7HS-10; 50 hp: NGK B8HS-10 (for Canada and Europe LIT-18616-01-81 lists BR7HS-10 and BR8HS-10); qty 3 |
| 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 | 800 ± 50 rpm |
| Thermostat | Opens at 48 to 52 °C (118 to 126 °F); fully open at 60 °C (140 °F); valve lift 3 mm (0.12 in) |
| Anodes | Inspect the anode, the trim tab and the bracket bottom anode: clean scale, oil or grease; replace if worn. Do not oil, grease or paint. |
| Propeller nut (M16) | 35 N·m (3.5 m·kg, 25 ft·lb) in LIT-18616-02-65; If the nut does not line up with the cotter pin hole, turn it in further |
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 (break-in)
Replace: gear case oil, gear case plug gaskets, propeller cotter pin
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, 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 40TR, 50TR service manual LIT-18616-02-65. Specs can change by model year and serial number, so always confirm your exact model from the serial tag on the clamp bracket.