Honda B75 twin (7.5 hp) service guide
Oil, gear oil, spark plugs and the service schedule for the Honda B75 twin (7.5 hp) (7.5 hp, four-stroke), from the factory service manual, plus how we service it in Hawaiʻi.
Models covered: Honda Marine Engine model B75, 4-cycle watercooled. 4 cycle, 2 cylinder, OHC, 149 cc (9.09 cu in), bore and stroke 50 x 38 mm, 7.5 ps at 6,000 rpm, recoil starter, flywheel magneto with breaker points, forced lubrication by trochoid pump, water cooled, diaphragm fuel pump, S type (transom 380 mm, 15 in) and L type (533 mm, 21 in), reduction ratio 13 : 25, dog clutch with forward, neutral and reverse.
Quick answers
- How much oil does a Honda B75 twin take?
- 0.8 L (1.7 US pt, 1.4 Imp pt). One figure only; there is no cartridge oil filter.
- What engine oil does a Honda B75 twin use?
- API Standard SD, SAE 10W-30.
- What gear oil does a Honda B75 twin use, and how much?
- API Standard GL-4, SAE 90 outboard motor gear oil. Quantity: 0.15 L (0.32 US pt, 0.26 Imp pt); fill through the oil filler hole until the oil emerges from the level bolt hole.
- What spark plug does a Honda B75 twin use?
- NGK D-5HS, qty 2. Gap: 0.6 to 0.7 mm.
- When should the water pump impeller be replaced on a Honda B75 twin?
- 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 Honda B75 twin?
- 1200 rpm, set with the stop screw with water circulating through the engine; pilot screw set for the highest rpm.
- What is the propeller nut torque on a Honda B75 twin?
- Held by a 14 mm plain washer, a new 3 mm split pin and the propeller cap; bend the pin ends around the cap. No nut torque. 2 blades, 210 x 150 mm (8.27 x 5.90 in).
Maintenance specs
| Engine oil | API Standard SD, SAE 10W-30 |
|---|---|
| Engine oil quantity | 0.8 L (1.7 US pt, 1.4 Imp pt). One figure only; there is no cartridge oil filter |
| Gear oil | API Standard GL-4, SAE 90 outboard motor gear oil |
| Gear oil quantity | 0.15 L (0.32 US pt, 0.26 Imp pt); fill through the oil filler hole until the oil emerges from the level bolt hole |
| Gear oil filler and level bolts | Oil filler hole (lower) and level bolt hole (upper) on the gearcase |
| Spark plug | NGK D-5HS, qty 2 |
| Spark plug gap | 0.6 to 0.7 mm |
| Idle speed | 1200 rpm, set with the stop screw with water circulating through the engine; pilot screw set for the highest rpm |
| Propeller | Held by a 14 mm plain washer, a new 3 mm split pin and the propeller cap; bend the pin ends around the cap. No nut torque. 2 blades, 210 x 150 mm (8.27 x 5.90 in) |
| Tappet clearance | 0.06 mm, with the "T" timing mark at the index mark on the starter case and the rocker arms in the free cycle; screw adjuster and lock nut. |
| Timing belt | Toothed belt from the timing pulley to the cam pulley. Do not cut, fold or twist the belt. Timing pulley 22 mm special nut 200 to 250 kg-cm (14.4 to 17.1 ft-lb), lock washer bent up; cam pulley 6 mm bolt 90 to 120 kg-cm (6.51 to 8.68 ft-lb) |
Source: Honda Marine Engine model B75 shop manual. Specs can change by model year and serial number, so always confirm your exact model from the serial tag on the clamp bracket.