Yamaha 25J / 30D (USA 25X / 30X) two-stroke service guide
Oil, gear oil, spark plugs and the service schedule for the Yamaha 25J / 30D (USA 25X / 30X) two-stroke (25 to 30 hp, two-stroke), from the factory service manual, plus how we service it in Hawaiʻi.
Models covered: 25J and 30D two-stroke triples (cover: USA and Canada 25X, 30X): 3 cylinders, 496 cm³ (30.3 cu in), 59.5 x 59.5 mm, 3 carburetors. 25 hp, approval model code 6K9: 25JMH (USA and Canada 25MH3, starting serial S: 201001, L: 500376), 25JMHO (S: 002915, L: 301291), 25JEHO (Canada 25EH; S: 550101, L: 600101), 25JEO (S: 101595, L: 403146), 25JETO (Canada 25TR3; L: 700101). 30 hp, approval model code 6J8: 30DMH (S: 004688, L: 305266, Y: 600416), 30DMHO (USA and Canada 30MH; S: 109639, L: 408394), 30DWH (L: 537036, Y: 641006, X: 740451), 30DEHO (30EH; L: 760756), 30DMO (S: 251193, L: 550886), 30DE (L: 355074), 30DEO (30ER; S: 156169, L: 462358), 30DET (L: 070101), 30DETO (30TR; L: 650101). Models with an O at the end of the name are oil injected; 25JMH, 30DMH, 30DWH, 30DE and 30DET are premix.
Quick answers
- What two-stroke oil does a Yamaha 25J / 30D two-stroke use?
- 2-stroke engine oil, grade TC-W3.
- What is the fuel to oil ratio for a Yamaha 25J / 30D two-stroke?
- Premix models (25JMH, 30DMH, 30DWH, 30DE, 30DET): mixing ratio 100:1. Oil injected models: no ratio (injected). Use a 50:1 fuel mixture to start the engine for the predelivery check and the oil injection pump test.
- What gear oil does a Yamaha 25J / 30D two-stroke use, and how much?
- Hypoid gear oil, SAE #90. Quantity: 200 cm³ (6.76 US oz, 7.04 Imp oz); fill through the oil-drain hole until it overflows from the oil-level hole with the motor straight up.
- What spark plug does a Yamaha 25J / 30D two-stroke use?
- NGK B7HS-10 or BR7HS-10 (noise suppressor type), qty 3. Gap: 0.9 to 1.0 mm (0.035 to 0.039 in).
- How often should a Yamaha 25J / 30D 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 25J / 30D 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 25J / 30D two-stroke?
- 750 ± 50 r/min; 1,050 ± 50 r/min on PTT models. Trolling speed 650 ± 50 r/min; 800 ± 50 r/min on PTT models. Neutral opening limit 3,750 ± 50 rpm.
- What is the propeller nut torque on a Yamaha 25J / 30D two-stroke?
- 35 N·m (3.5 m·kgf, 25 ft·lb); if the cotter pin hole does not line up, turn the nut further in.
Maintenance specs
| Two-stroke engine oil | 2-stroke engine oil, grade TC-W3 |
|---|---|
| Fuel to oil ratio | Premix models (25JMH, 30DMH, 30DWH, 30DE, 30DET): mixing ratio 100:1. Oil injected models: no ratio (injected). Use a 50:1 fuel mixture to start the engine for the predelivery check and the oil injection pump test |
| Gear oil | Hypoid gear oil, SAE #90 |
| Gear oil quantity | 200 cm³ (6.76 US oz, 7.04 Imp oz); fill through the oil-drain hole until it overflows from the oil-level hole with the motor straight up |
| Gear oil drain and level plugs | Refit the oil-level plug first, then the drain plug |
| Lower unit holding pressure | 100 kPa (1.0 kg/cm², 14.2 psi) at the oil-level hole with the drain screw tight, must hold 10 seconds; do not over-pressurize. Tester YB-35956 / 90890-06756 |
| Spark plug | NGK B7HS-10 or BR7HS-10 (noise suppressor type), qty 3 |
| Spark plug gap | 0.9 to 1.0 mm (0.035 to 0.039 in) |
| Spark plug torque (M14) | 20 N·m (2.0 m·kgf, 14 ft·lb) |
| Idle speed | 750 ± 50 r/min; 1,050 ± 50 r/min on PTT models. Trolling speed 650 ± 50 r/min; 800 ± 50 r/min on PTT models. Neutral opening limit 3,750 ± 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 and replace if worn out; clean scale off with a wire brush and polish the mount contact surface; never paint. The trim tab is fitted new when the lower unit is installed. |
| Propeller nut (M14) | 35 N·m (3.5 m·kgf, 25 ft·lb); if the cotter pin hole does not line up, turn the nut further in |
| Power trim and tilt fluid (PTT models) | ATF Dexron II; fluid level directly below the level checking hole with the motor fully tilted up; reservoir plug (M10) 7 N·m (0.7 m·kgf, 5.1 ft·lb); the unit is bled by running the tilt rod up and down under power |
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
Check: spark plugs, fuel filter, anodes
Initial 50 hours (3 months)
Replace: gear case plug gaskets, propeller cotter pin
Check: spark plugs, 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 25J, 30D service manual. Specs can change by model year and serial number, so always confirm your exact model from the serial tag on the clamp bracket.