Yamaha T8 High Thrust (T8 / FT8D) service guide
Oil, gear oil, spark plugs and the service schedule for the Yamaha T8 High Thrust (T8 / FT8D) (8 hp, four-stroke), from the factory service manual, plus how we service it in Hawaiʻi.
Models covered: T8MH (FT8DMH), T8ER (FT8DE), T8PR (FT8DEP), T8PH (FT8DEHP). Four-stroke 2 cylinder SOHC, 197 cm³ (F8 powerhead), high thrust 2.92 gear ratio. Model code 69G. Starting serials: T8MH L 350101 / X 650101; T8ER L 400101 / X 700101; T8PR L 500101 / X 750101; T8PH L 550101 / X 850101 (supp. 1).
Quick answers
- How much oil does a Yamaha T8 High Thrust take?
- 800 cm³ (27.0 US oz, 28.2 Imp oz).
- What engine oil does a Yamaha T8 High Thrust use?
- 4-stroke engine oil, API SE, SF, SG or SH, SAE 10W-30 or 10W-40.
- What gear oil does a Yamaha T8 High Thrust use, and how much?
- Hypoid gear oil, GL-4 (SAE #90). Quantity: 320 cm³ (10.9 US oz, 11.3 Imp oz).
- What spark plug does a Yamaha T8 High Thrust use?
- BR6HS-10. Gap: 0.9 to 1.0 mm (0.035 to 0.039 in).
- How often should a Yamaha T8 High Thrust be serviced?
- The factory schedule lists: Initial 10 hours; 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 T8 High Thrust?
- 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 T8 High Thrust?
- 1,050 ± 50 r/min.
- What is the propeller nut torque on a Yamaha T8 High Thrust?
- 17 N·m (1.7 kgf·m, 12.5 ft·lb); split pin.
Maintenance specs
| Engine oil | 4-stroke engine oil, API SE, SF, SG or SH, SAE 10W-30 or 10W-40 |
|---|---|
| Engine oil quantity | 800 cm³ (27.0 US oz, 28.2 Imp oz) |
| Engine oil drain plug | 24 N·m (2.4 kgf·m, 17.8 ft·lb) |
| Gear oil | Hypoid gear oil, GL-4 (SAE #90) |
| Gear oil quantity | 320 cm³ (10.9 US oz, 11.3 Imp oz) |
| Gear oil level check and drain plugs | 7 N·m (0.7 kgf·m, 5.1 ft·lb) |
| Lower unit holding pressure | 100 kPa (1.0 kgf/cm², 14.2 psi) |
| Spark plug | BR6HS-10 |
| Spark plug gap | 0.9 to 1.0 mm (0.035 to 0.039 in) |
| Spark plug torque | 25 N·m (2.5 kgf·m, 18.4 ft·lb) |
| Idle speed | 1,050 ± 50 r/min |
| Thermostat | Full close 60 °C (140 °F); opens 58 to 62 °C (136.4 to 143.6 °F); fully open 70 °C (158 °F); lift 3 mm (0.12 in) |
| Anodes | Engine anode plug M16 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). Anodes on the engine, clamp bracket and lower unit. |
| Propeller nut (STD) | 17 N·m (1.7 kgf·m, 12.5 ft·lb); split pin |
| Power tilt (PT models) | ATF Dexron II, level just below the check hole; reservoir cap 5 N·m (0.5 kgf·m, 3.6 ft·lb); cylinder end screw and tilt piston 45 N·m (4.5 kgf·m, 32 ft·lb) |
| Valve clearance, cold | Intake 0.15 to 0.20 mm (0.006 to 0.008 in); exhaust 0.20 to 0.25 mm (0.008 to 0.010 in); rocker arm locknut 8 N·m (0.8 kgf·m, 5.9 ft·lb) |
| Timing belt | Check/replace every 100 hours (6 months) |
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
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: spark plugs, 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: spark plugs, fuel filter, anodes
Every 200 hours (1 year)
Replace: engine oil, 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 T8PH/T8PR supplementary 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.