Honda BF15D / BF20D service guide
Oil, gear oil, spark plugs and the service schedule for the Honda BF15D / BF20D (15 to 20 hp, four-stroke), from the factory service manual, plus how we service it in Hawaiʻi.
Models covered: BF15D (code BALJ) and BF20D (BAMJ), types SH, SHS, SR, LH, LHS, LR; 4-stroke twin, 350 cm³, single carburetor, CDI.
Quick answers
- How much oil does a Honda BF15D / BF20D take?
- 1.0 L (1.06 US qt) oil change; 1.3 L (1.37 US qt) with filter.
- What engine oil does a Honda BF15D / BF20D use?
- SAE 10W-30, API SG, SH or SJ.
- What gear oil does a Honda BF15D / BF20D use, and how much?
- SAE #90 hypoid gear oil or equivalent.
- What spark plug does a Honda BF15D / BF20D use?
- NGK CR5EH-9 or Denso U16FER9, qty 2. Gap: 0.8 to 0.9 mm (0.031 to 0.035 in).
- How often should a Honda BF15D / BF20D be serviced?
- The factory schedule lists: First month or 20 hours; Every 6 months or 100 hours; Every year or 200 hours. 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 Honda BF15D / BF20D?
- 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 BF15D / BF20D?
- 900 ± 50 r/min in neutral (oil at 50 to 60 °C).
- What is the propeller nut torque on a Honda BF15D / BF20D?
- 1 N·m (0.1 kgf·m, 0.7 lbf·ft), then tighten until the cotter pin fits, maximum 35 N·m (3.5 kgf·m, 25 lbf·ft); new stainless cotter pin.
Maintenance specs
| Engine oil | SAE 10W-30, API SG, SH or SJ |
|---|---|
| Engine oil quantity | 1.0 L (1.06 US qt) oil change; 1.3 L (1.37 US qt) with filter |
| Oil filter | Hand tight until the O-ring touches, then 7/8 turn more with wrench 07HAA-PJ70100; 12 N·m (1.2 kgf·m, 8.7 lbf·ft) |
| Gear oil | SAE #90 hypoid gear oil or equivalent |
| Gear oil drain and check bolts | 3.5 N·m (0.35 kgf·m, 2.5 lbf·ft) |
| Spark plug | NGK CR5EH-9 or Denso U16FER9, qty 2 |
| Spark plug gap | 0.8 to 0.9 mm (0.031 to 0.035 in) |
| Spark plug torque | 12 N·m (1.2 kgf·m, 9 lbf·ft). Procedure: new plug 1/2 turn after seating, reused plug 1/8 to 1/4 turn |
| Idle speed | 900 ± 50 r/min in neutral (oil at 50 to 60 °C) |
| Thermostat | Starts opening 60 °C; fully open 70 °C (158 °F); lift more than 3.0 mm (0.12 in) |
| Gear case anode nut | 6 mm self-locking nut 10 N·m (1.0 kgf·m, 7 lbf·ft); do not reuse the nut |
| Propeller castle nut | 1 N·m (0.1 kgf·m, 0.7 lbf·ft), then tighten until the cotter pin fits, maximum 35 N·m (3.5 kgf·m, 25 lbf·ft); new stainless cotter pin |
| Valve clearance, cold | IN 0.15 to 0.19 mm; EX 0.21 to 0.25 mm; lock nut 8 N·m (0.8 kgf·m, 5.8 lbf·ft) |
| Timing belt | Inspect; replace if worn or damaged; replace if oily (no deflection spec) |
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.
First month or 20 hours
Replace: engine oil, oil drain plug gasket, gear case oil, gear case plug gaskets
Every 6 months or 100 hours
Replace: engine oil, oil drain plug gasket, gear case oil, gear case plug gaskets
Check: spark plugs, fuel filter
Every year or 200 hours
Replace: engine oil, oil filter, oil drain plug gasket, spark plugs, fuel filter, gear case oil, gear case plug gaskets, water pump impeller
Check: thermostat
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: Honda BF15D/BF20D Shop Manual, part no. 66ZY000. Specs can change by model year and serial number, so always confirm your exact model from the serial tag on the clamp bracket.