Suzuki DT25 / DT30 three-cylinder two-stroke (1988-2000, oil injected) service guide
Oil, gear oil, spark plugs and the service schedule for the Suzuki DT25 / DT30 three-cylinder two-stroke (1988-2000, oil injected) (25 to 30 hp, two-stroke), from the factory service manual, plus how we service it in Hawaiʻi.
Models covered: DT25, 1988 to 2000, and DT30, 1988 to 1997: inline 3 cylinder, 33.1 cu in (543 cc), bore and stroke 2.44 x 2.36 in, oil injection, Digital I.C.
Quick answers
- What two-stroke oil does a Suzuki DT25 / DT30 three-cylinder 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 DT25 / DT30 three-cylinder 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 DT25 / DT30 three-cylinder two-stroke use, and how much?
- Suzuki Outboard Motor Gear Oil or an equivalent high quality SAE 90 hypoid gear oil. Quantity: 7.8 oz (230 ml).
- What spark plug does a Suzuki DT25 / DT30 three-cylinder two-stroke use?
- DT25 1990: NGK BR7HS-10; DT25 1991: NGK BR7HS (Champion L5, L7J); DT25 1992-00: NGK BR7HS-10. DT30 1989-97: NGK BR7HS-10 (1988 is not listed). Qty 3. Gap: 0.035 to 0.039 in (0.9 to 1.0 mm).
- How often should a Suzuki DT25 / DT30 three-cylinder 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 DT25 / DT30 three-cylinder two-stroke?
- The factory schedule says to inspect it at 10 hours and 100 hours. 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 Suzuki DT25 / DT30 three-cylinder two-stroke?
- DT25 1990: 650 to 700 rpm; DT25 1991-00: 600 to 650 rpm. DT30: 650 to 700 rpm.
- What is the propeller nut torque on a Suzuki DT25 / DT30 three-cylinder two-stroke?
- DT25C, DT30C: 21 to 22.5 ft-lb (29 to 31 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 | 7.8 oz (230 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 | DT25 1990: NGK BR7HS-10; DT25 1991: NGK BR7HS (Champion L5, L7J); DT25 1992-00: NGK BR7HS-10. DT30 1989-97: NGK BR7HS-10 (1988 is not listed). Qty 3 |
| Spark plug gap | 0.035 to 0.039 in (0.9 to 1.0 mm) |
| 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 | DT25 1990: 650 to 700 rpm; DT25 1991-00: 600 to 650 rpm. DT30: 650 to 700 rpm |
| Propeller nut | DT25C, DT30C: 21 to 22.5 ft-lb (29 to 31 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
Check: water pump impeller
Every 50 hours or 3 months
Replace: gear case plug gaskets, propeller cotter pin
Check: anodes
Every 100 hours or 6 months
Replace: gear case oil, gear case plug gaskets, propeller cotter pin
Check: spark plugs, fuel filter, water pump impeller, 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
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: 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.