Suzuki DT35 / DT40 two-stroke (1988-1998, oil injected) service guide
Oil, gear oil, spark plugs and the service schedule for the Suzuki DT35 / DT40 two-stroke (1988-1998, oil injected) (35 to 40 hp, two-stroke), from the factory service manual, plus how we service it in Hawaiʻi.
Models covered: DT40, 1988 to 1998: inline 2 cylinder, 42.5 cu in (696 cc), bore and stroke 3.11 x 2.80 in, oil injection, Suzuki P.E.I. The tune-up section treats the DT35 and DT40 together as 2-cylinder engines.
Quick answers
- What two-stroke oil does a Suzuki DT35 / DT40 two-stroke use?
- Suzuki CCI oil or an NMMA certified 2-stroke lubricant; if neither is available, use only 2-stroke outboard oil.
- What is the fuel to oil ratio for a Suzuki DT35 / DT40 two-stroke?
- Oil injection, variable ratio: about 150:1 fuel to oil at idle, changing gradually to 50:1 at full throttle.
- What gear oil does a Suzuki DT35 / DT40 two-stroke use, and how much?
- Suzuki Outboard Motor Gear Oil or an equivalent high quality SAE 90 hypoid gear oil. Quantity: 20.6 oz (610 ml).
- What spark plug does a Suzuki DT35 / DT40 two-stroke use?
- NGK B8HS: DT35 1988-89 (Champion L4J, RL4J, L78, RL78), DT40 1988-98. Qty 2. Gap: 0.031 to 0.035 in.
- How often should a Suzuki DT35 / DT40 two-stroke be serviced?
- The factory schedule lists: First 10 hours or 1 month; Every 50 hours or 3 months; Every 100 hours or 6 months. 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 Suzuki DT35 / DT40 two-stroke?
- The factory schedule says to replace it at 100 hours, and we follow that. In any case we never let it go longer than a year in Hawaiʻi's salt water.
- What is the idle speed of a Suzuki DT35 / DT40 two-stroke?
- 650 to 700 rpm.
- What is the propeller nut torque on a Suzuki DT35 / DT40 two-stroke?
- 36 to 43.5 ft-lb (50 to 60 N·m).
Maintenance specs
| Injection oil | Suzuki CCI oil or an NMMA certified 2-stroke lubricant; if neither is available, use only 2-stroke outboard oil |
|---|---|
| Oil tank | 2.1 quarts (2.0 liters) |
| Fuel to oil ratio | Oil injection, variable ratio: about 150:1 fuel to oil at idle, changing gradually to 50:1 at full throttle. |
| Gear oil | Suzuki Outboard Motor Gear Oil or an equivalent high quality SAE 90 hypoid gear oil |
| Gear oil quantity | 20.6 oz (610 ml). |
| Gear oil drain (fill) plug and oil level plug | Loosen the oil level plug first, then remove the fill (drain) plug at the lower end of the gear housing, then the oil level plug. Check the magnet end of the drain screw for metal. Use new gaskets (washers); install the oil level and vent plugs (if fitted) first, then the fill plug. |
| Lower unit pressure test | 16 to 18 psi of air, submerged or sprayed with soapy water; then 3 to 5 inches of vacuum; hold each for a few minutes |
| Spark plug | NGK B8HS: DT35 1988-89 (Champion L4J, RL4J, L78, RL78), DT40 1988-98. Qty 2 |
| Spark plug gap | 0.031 to 0.035 in |
| Spark plug torque | 10 to 15 ft-lb (14 to 20 N·m) with a new crush washer, or about 1/4 turn to crush the washer. |
| Idle speed | 650 to 700 rpm |
| Propeller nut | 36 to 43.5 ft-lb (50 to 60 N·m) |
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 10 hours or 1 month
Replace: gear case oil, gear case plug gaskets, propeller cotter pin
Every 50 hours or 3 months
Replace: gear case plug gaskets
Check: fuel filter, anodes
Every 100 hours or 6 months
Replace: gear case oil, gear case plug gaskets, propeller cotter pin, water pump impeller
Check: spark plugs, fuel filter, anodes
Every 200 hours or 1 year (our Hawai‘i yearly service) Hawai‘i
Replace: gear case oil, gear case plug gaskets, propeller cotter pin, water pump impeller
Check: spark plugs, fuel filter, anodes
Source: Suzuki DT 2 to 225 hp two-stroke outboards 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.