The Suzuki DF25A and DF30A are the same engine. The owner's manual gives both one specification block: three cylinders, 490 cm³ (29.9 cu in), 60.4 × 57.0 mm (2.38 × 2.24 in) bore and stroke, 1.5 L of engine oil, approximately 0.33 L of gear oil, the same spark plug, the same fuses and the same battery requirement. The service manual adds that they share a 10.1 : 1 compression ratio, an 11 : 23 (2.09) gear ratio, the same propeller list, the same transom heights and the same weights, version for version. What separates them is the ECM, which the service manual states is different for the two motors: maximum output of 18.4 kW (25 PS) against 22.1 kW (30 PS), a full-throttle operating range of 5000–6000 r/min against 5300–6300 r/min, and an over-revolution limiter of 6200 r/min against 6400 r/min.
The other real difference is which versions you can buy. The DF25A is offered in short and long shaft, manual or electric start, manual tilt or power trim and tilt, tiller or remote. The DF30A, as we sell it, is long shaft only, electric start only, always with power trim and tilt, tiller or remote. If you need a 15 in transom height, a pull-start motor or the lightest motor on the transom, only the DF25A is offered that way. If you are putting a 20 in shaft, electric-start, power-tilt motor on a boat rated for 30 hp, a DF30AT weighs exactly what a DF25AT weighs in the service manual, so the extra output costs nothing on the scale.
Spec table: DF25A vs DF30A
Figures are from the 2019 owner's manual (99011-94L60-03B), the service manual (99500-94L10-01E, with its 2024 tightening-torque supplement) and the DF25A/30A row of Suzuki's 2025 maintenance manual. Where two documents differ, both are shown. The service manual's model prefixes are 02504F for the DF25A and 03003F for the DF30A.
| Specification | DF25A | DF30A |
|---|---|---|
| Maximum output | 18.4 kW (25 PS) | 22.1 kW (30 PS) |
| Full-throttle operating range | 5000–6000 r/min | 5300–6300 r/min |
| Over-revolution limiter (service manual) | 6200 r/min | 6400 r/min |
| ECM | DF25A-specific | DF30A-specific |
Everything else in the specification is shared:
| Specification | DF25A and DF30A |
|---|---|
| Idle speed (neutral) | 850 ± 50 r/min; factory adjusted between 800–900 r/min |
| Engine | 4-stroke SOHC, 3 cylinders, electronic fuel injection, Digital CDI ignition |
| Displacement | 490 cm³ (29.9 cu in owner's manual; 29.90 cu in service manual) |
| Bore × stroke | 60.4 × 57.0 mm (2.38 × 2.24 in) |
| Compression ratio | 10.1 : 1 |
| Gear ratio | 11 : 23 (2.09) |
| Engine oil capacity | 1.5 L (1.6/1.3 US/Imp qt) oil change only; 1.7 L (1.8/1.5 US/Imp qt) with oil filter change |
| Gear oil capacity | Approx. 0.33 L (0.3/0.3 US/Imp qt) owner's manual; 330 ml (11.1/11.6 US/Imp oz) service manual |
| Spark plug | NGK MR6K-9 (2019 owner's manual); NGK CPR6EA-9 (service manual); gap 0.8–0.9 mm (0.031–0.035 in); resistor type only |
| Valve clearance (cold) | IN 0.18–0.22 mm (0.007–0.009 in); EX 0.20–0.24 mm (0.008–0.009 in) |
| Thermostat | 58–62 °C (136–144 °F); part 17670-94J02 for 2015 and later (2025 maintenance manual) |
| Battery charge coil output | 168 W (12 V) |
| Fuses | Main 30 A (all electric start models); ECM 10 A (DF25AT/25AR/30AT remote control models) |
| Battery, electric start | 650 MCA/ABYC, or 512 CCA/SAE, or 160 RC minutes/SAE (owner's manual); the service manual adds 12 V 70 AH |
| Transom height | S 422 mm (15 in type); L 549 mm (20 in type); no X version |
| Propeller sizes (service manual) | 3 × 10¼ × 9, 10, 11, 12, 13, 14 or 15 in |
| Propeller nut torque | 20–30 N·m (2.0–3.0 kg-m, 14.5–21.5 lb-ft) owner's manual; 25 N·m (2.5 kgf-m, 18.0 lbf-ft) service manual |
| Cylinder compression (service manual reference) | Recoil start 500–1000 kPa (71–142 psi); starter motor 500–1800 kPa (71–256 psi); maximum difference between cylinders 100 kPa (14 psi) |
What actually changes
Output and full-throttle range
Each model has its own full-throttle operating range, and that range is what you prop to: 5000–6000 r/min on the DF25A, 5300–6300 r/min on the DF30A. The two share one propeller list, so the difference is which pitch lands the engine in range on your hull; the owner's manual's rule is that smaller loads generally require larger-pitch propellers and larger loads smaller-pitch propellers. The method is on our full-throttle RPM and propeller guide; the genuine Suzuki propeller for the DF25A/30A fits both.
Rev limiter
The service manual sets the over-revolution limiter at 6200 r/min on the DF25A and 6400 r/min on the DF30A. The owner's manual describes the caution the same way for both: it activates when engine speed exceeds the maximum recommended speed for more than 10 seconds, engine speed is automatically reduced to approximately 3000 r/min, and the red caution lamp does not light (on a remote control model the buzzer in the control box beeps). Reset it by moving the throttle to idle for about four seconds. Consult your authorized Suzuki marine dealer if it activates for no apparent reason.
The ECM
"ECM is different for DF25A and DF30A" is the only hardware difference the service manual names. Neither manual describes converting one model into the other, so treat the ECM as model-specific and order parts by the model code and serial number on the ID plate.
Variants: reading the model code
The suffix after the model number is the configuration. As the store's listings use them: S is short shaft, L is long shaft, E is electric start, T is power trim and tilt with remote control, TH is power trim and tilt with a tiller, and W is white. The 2019 owner's manual splits the lineup the same way: DF25A and DF25ATH/30ATH are tiller handle models, DF25AR and DF25AT/30AT are remote control models, the DF25A/25AR have manual tilt and the DF25AT/25ATH/30AT/30ATH have power trim and tilt. In that manual the DF30A appears only as the DF30AT and DF30ATH. The service manual also lists DF30A, DF30AE, DF30AR, DF30AQ and DF30AQE and the matching DF25AQ/AQE, none of which are in the 2019 owner's manual or the store's lineup.
What is offered for each
| Configuration | DF25A | DF30A |
|---|---|---|
| Short shaft, manual start, manual tilt, tiller | DF25AS5 | Not offered |
| Short shaft, electric start, manual tilt, tiller | DF25AES5 | Not offered |
| Short shaft, electric start, power trim and tilt, remote | DF25ATS5 (white DF25ATSW5) | Not offered |
| Long shaft, electric start, power trim and tilt, remote | DF25ATL5 (white DF25ATLW5) | DF30ATL5 (white DF30ATLW5) |
| Short shaft, electric start, power trim and tilt, tiller | DF25ATHS5 (white DF25ATHSW5) | Not offered |
| Long shaft, electric start, power trim and tilt, tiller | DF25ATHL5 (white DF25ATHLW5) | DF30ATHL5 (white DF30ATHLW5) |
So the manual-tilt DF25A versions are short shaft only, and every DF30A is a long-shaft, electric-start, power-trim-and-tilt motor. Short shaft is the 422 mm (15 in type) transom height; long shaft is 549 mm (20 in type). Measure before you order: how to measure for shaft length.
Weight by version
The service manual prints one weight table, without engine oil, and repeats it unchanged under the DF30A versions.
| Version | S (15 in) | L (20 in) |
|---|---|---|
| DF25A / DF30A (tiller, manual start, manual tilt) | 62 kg (137 lb) | 63 kg (139 lb) |
| DF25AE / DF30AE (tiller, electric start, manual tilt) | 65 kg (143 lb) | 66 kg (145 lb) |
| DF25AR / DF30AR (remote, manual tilt) | 63 kg (139 lb) | 64 kg (141 lb) |
| DF25AQ / DF30AQ (service manual only) | 69 kg (152 lb) | 70 kg (154 lb) |
| DF25AQE / DF30AQE (service manual only) | 72 kg (159 lb) | 73 kg (161 lb) |
| DF25ATH / DF30ATH (tiller, power trim and tilt) | 73 kg (161 lb) | 74 kg (163 lb) |
| DF25AT / DF30AT (remote, power trim and tilt) | 71 kg (157 lb) | 72 kg (159 lb) |
Read against the store lineup: the DF25AS5 at 62 kg (137 lb) is the lightest motor in either range, and the lightest DF30A sold is the DF30ATL5 at 72 kg (159 lb). Power trim and tilt, not horsepower, is what adds weight.
Manual tilt vs power trim and tilt
On the manual-tilt DF25A/25AR you set trim angle by moving the tilt pin (toward the boat to lower the bow, away from it to raise the bow), tilt by hand with the release lever in the release position until the tilt up lock arm catches, and get two shallow water positions for very low speeds only. On the power trim and tilt models you trim with the switch, there is a manual release screw (two turns counterclockwise) for tilting by hand, and the tilt lock lever is for stationary support only, never for trailering. In shallow water on PTT models, do not operate the engine above 1500 r/min or on plane with the engine beyond the maximum trim position; the water intake holes may be above the water line. The PTT switch also works with the ignition key off, so keep people clear of the motor. Procedures are on our tilt, trim and shallow water drive page; if the system stops working, start with power trim and tilt troubleshooting.
What does not change
- Engine oil: SAE 10W-40 or 10W-30 Suzuki Marine 4-Cycle Engine Oil (ECSTAR) or equivalent. Change at the initial 20 hours (1 month), then every 100 hours (12 months); replace the filter at 20 hours, then every 200 hours (12 months). See the Suzuki oil capacity chart.
- Gear oil: Suzuki Hypoid Gear Oil, or SAE 90 hypoid rated API GL-5, at the initial 20 hours (1 month) and every 100 hours (12 months). Milky oil means water: contact your dealer and do not run the motor until the oil is changed and the cause corrected.
- Spark plug: one plug for both, by manual year (table above); resistor type only.
- Cooling: inspect the water pump and impeller every 200 hours (12 months) and replace the impeller every 300 hours (36 months); inspect the thermostat every 100 hours (12 months). The 58–62 °C thermostat 17670-94J02 is the part for both.
- Battery (electric start): 650 MCA, or 512 CCA, or 160 RC minutes minimum; never a deep-cycle battery as the main cranking battery. A recoil-start DF25A needs a 70 AH or larger battery, rectifier and related items only if you want electrical accessories. See which battery a 25 or 30 hp Suzuki needs.
- Break-in: 10 hours, the same schedule for both.
Intervals, procedures and torque figures for both motors are collected in our DF25A/DF30A service guide.
Which one to buy
- Boat rated for 25 hp: the DF25A, and it is the only one of the two sold with manual start, a 15 in transom height or manual tilt. The capacity plate decides; see what size outboard your boat needs.
- Boat rated for 30 hp with a 20 in transom: if you want electric start and power trim and tilt anyway, the DF30A is the same motor at the same weight with 22.1 kW (30 PS) instead of 18.4 kW (25 PS) and a 5300–6300 r/min range. The DF25ATL5 and DF25ATHL5 fill the same slot at 25 hp; nothing in the manuals separates them from the DF30A except output, operating range, the limiter and the ECM itself.
- Lightest and simplest: the DF25AS5 at 62 kg (137 lb), with no battery needed to start it. Electric-start motors need a battery that meets the specification above; remote control models add the 10 A ECM fuse.
- Tiller or remote: a remote AT motor is 71 kg (157 lb) short or 72 kg (159 lb) long against 73 kg (161 lb) and 74 kg (163 lb) for the tiller ATH. The owner's manual gives a removal procedure for tiller handle models but recommends having your authorized Suzuki marine dealer remove a remote control model from the boat.
Parts for these motors
Boat Max Online is an authorized Suzuki, Honda and Yamaha Marine dealer and sells complete Suzuki outboards up to 30 hp, with free shipping on motors and on orders over $149 to the lower 48. Shop every version above in our Suzuki 25 hp and Suzuki 30 hp collections. For either motor we carry the genuine DF25A/30A propeller, the oil change kit, the 58–62 °C thermostat and the complete DF25A/30A lower unit assembly (special order, non-returnable). Have the model code and serial number from the ID plate ready and we will confirm fitment.
Sources: Suzuki owner's manual for DF25A/DF30A (99011-94L60-03B, 2019); Suzuki service manual 99500-94L10-01E (DF25A/DF30A, with the 2024 tightening torque supplement); Suzuki 4-Stroke Outboard Maintenance Manual, 2025 edition. Figures are Suzuki's published values; confirm against the manual for your model year and serial number.