Most Suzuki four-strokes from the DF8A up can be flushed two ways: through the flush port with the engine stopped (garden hose on, about five minutes, no engine running), or with a flushing attachment (muffs) with the engine running at idle for a few minutes, propeller removed. Suzuki's owner's manuals call the engine-running muffs method the recommended one on most families, but the flush-port method is the easier one to get right and needs no engine start. The two smallest portables, the DF2.5 and the DF4A/DF6A, are flushed by running them in a container of fresh water; the DF4A/DF6A also has a flush plug that takes an optional attachment.
Whatever the method, the manual's rule for when to do it is the same: after operation in muddy, brackish or salt water, flush the water passages and the motor surface with clean, fresh water. Salt left in the passages corrodes the motor and shortens its life.
Which method your Suzuki supports
This table is built from the owner's manuals we have on file. Where the manual we have does not describe a method, the cell says so; check your own manual for the year and serial of your motor.
| Family (manual) | Flush port, engine stopped | Muffs, engine running | Tank or drum | Notes |
|---|---|---|---|---|
| DF2.5 (2019) | Not described | Not described | Yes, the only method given | Idle about five minutes in a container such as an empty 55 gallon drum, prop removed |
| DF4A / DF6A (2019, 2020–2024 models) | Yes, via the flush plug with an optional flushing attachment from your dealer | Not described | Yes, Suzuki's recommended method | Idle about five minutes in the drum; flush-port method about five minutes, engine stopped |
| DF8A / DF9.9A (2014) | Yes, one port | Yes, recommended | Not described | Full-tilt-up flush-port variant also given |
| DF9.9B / DF15A / DF20A (2014 and 2020) | Yes, one port | Yes, recommended | Not described | Full-tilt-up variant also given |
| DF25A / DF30A (2019 model year) | Yes, one port | Yes, recommended | Not described | Remove the propeller before fitting the muffs |
| DF40A / DF50A / DF60A (2022–2024) | Yes, one port | Yes, recommended | Not described | Tape the auxiliary water intake hole before muffs (except DF50AV/60AV) |
| DF75 / DF90A (2023) | Yes, two ports (plug A or C) | Not in the manual we have; check yours | Not described | Full-tilt-up variant also given |
| DF100A / DF115A / DF140A (2016) | Yes, one port | Yes, recommended; needs a commercially available engine flush device | Not described | Full-tilt-up variant also given |
| DF115B / DF140B (2022–2023, DF115BG/DF140BG manual) | Yes, plug A or C | Yes, recommended; needs a commercially available engine flush device | Not described | Full-tilt-up variant also given |
| DF150A / DF175A / DF200A (2020 and 2023–2024) | Yes, two ports (plug A or C), in both manuals | 2020 manual: yes, recommended. 2023–2024 manual: not printed; the flush port is the only method it gives | Not described | Full-tilt-up variant also given in both manuals |
| DF150AP / DF175AP / DF200AP (2020) | Yes, two ports (plug A or C) | Yes, recommended | Not described | Full-tilt-up variant also given |
| DF225 / DF250 (2022 model year) | Yes, two ports (plug A or C) | Yes, recommended | Not described | Full-tilt-up variant also given |
| DF250AP / DF300AP (2022 model year) | Yes, two ports (plug A or C) | Yes, recommended; requires the Suzuki genuine flushing attachment | Not described | Tape both STBD/PORT auxiliary water intakes before muffs |
| DF300B / DF350A (2023) | Yes, two ports (plug A or C) | Yes, recommended; requires the Suzuki genuine flushing attachment | Not described | Run on the attachment for 5 minutes rather than a few; full-tilt-up variant also given |
Method 1: flush port, engine stopped
The engine never runs, so there is no risk of a dry start and no propeller to remove. The port takes a standard garden hose thread.
- Make sure the motor is stopped and in the vertical position.
- Remove the plug from the flushing port. On the DF75/DF90A, DF150A/175A/200A, DF150AP/175AP/200AP, DF225/DF250, DF250AP/DF300AP and DF300B/DF350A there are two ports; remove one of plug A or C. The DF115B/DF140B manual likewise says to remove plug A or C.
- Install the garden hose directly, or through a hose connector matched to the flushing-point thread. Suzuki prints the thread as 0.75 – 11.5 NHR, the American standard hose coupling thread for garden hose applications. The DF25A/30A, DF40A–60A, DF100A–140A, DF115B/140B, DF150A–200A (2023–2024 manual) and DF300B/350A manuals add that the hose connector (flushing attachment) matched to the flushing-point thread is included in the crate parts, so if you bought the motor new it should be in the box.
- Turn on the water to obtain a good water flow. Flush the engine for about five minutes.
- Turn off the water.
- Remove the hose and connector, then reinstall the plug into the flushing port.
- Leave the motor in a vertical position until the engine is drained completely.
Flush-port with the motor tilted up
Every manual that gives the flush-port method also allows it with the motor at full tilt up, useful on a trailer. Raise the engine to the full tilt up position, follow the same steps as above, then lower the motor to a vertical position until the engine is drained completely. The manuals print this in capitals: DO NOT RUN ENGINE IN THE FULL TILT UP POSITION.
On the DF4A/DF6A the flush-port method exists too, but you need an optional flushing attachment from your authorized Suzuki Marine dealer that fits the flush plug port. Remove the flush plug, install the attachment, connect the hose, flush for about five minutes, then reinstall the plug and leave the motor vertical until drained.
Method 2: flushing attachment (muffs), engine running
Suzuki recommends this as the primary method on most families from the DF8A up because the pump circulates fresh water through the whole system, thermostat included. It only works if you respect the warnings. The manuals state that severe engine damage can occur in as little as 15 seconds if the engine is started without supplying water to the cooling system, so the water has to be on and flowing before you touch the starter.
- Make sure the motor is stopped.
- Remove the propeller. Every manual that gives this method has you run the motor with the propeller removed; the DF25A/30A manual puts it as step 2 before the muffs go on.
- DF40A/50A/60A (except DF50AV/60AV): cover the auxiliary water intake hole with a piece of duct tape. DF250AP/300AP: cover the STBD/PORT auxiliary water intake holes with duct tape. The tape stops the pump drawing air through the auxiliary intake.
- Install the flushing attachment so that the water intake holes are covered by the rubber cups on the attachment.
- Connect a garden hose and turn on the water so that plenty of excess water flows out from around the rubber cups.
- Shift into NEUTRAL (remote-control lever in NEUTRAL on remote models) and start the motor. As soon as the engine starts, water should spray out of the pilot water hole, indicating proper water pump operation. If no water spray is evident, stop the motor immediately and consult your dealer.
- Allow the engine to run only at idle speed while flushing. Readjust the water flow, if necessary, so that there is still plenty of excess water flowing out from around the rubber cups.
- Allow the water to continue circulating for a few minutes.
- Stop the motor, then turn off the water.
- Remove the flushing attachment, and the duct tape if you used it.
- Clean the motor surface and apply a coat of automotive wax.
Family-specific notes. On the DF100A/115A/140A and DF115B/140B the manual says you must obtain a commercially available engine flush device; on the DF250AP/300AP and DF300B/350A it says you must obtain the flushing attachment as a Suzuki genuine part. The DF300B/350A manual also runs the flush a little differently: install the attachment so that it covers the water intake hole, make sure cooling water is discharged from the water intake holes before you start and again while the engine idles, let the water circulate for 5 minutes rather than a few, and if the overheat buzzer sounds because the cooling water level is low, increase the cooling water flow. The 2023–2024 DF150A/175A/200A manual does not print this method at all; it gives only the flush port. If the muffs do not seal well on your gearcase, use the flush port instead.
No throttle. The manuals allow idle only on muffs, and a worn impeller shows itself here first; if you suspect yours is already worn, read the impeller replacement interval guide.
Method 3: tank or drum for the DF2.5 and DF4A/DF6A
The DF2.5 manual gives only this method, and the DF4A/DF6A manual calls it the recommended one. Both use the same steps.
- Make sure that the motor is stopped.
- Shift the motor into NEUTRAL.
- Remove the propeller from the motor.
- Install the motor on a large container such as an empty 55 gallon drum.
- Fill the container with clean, fresh water as the manual's illustration shows, deep enough that the water intake holes are under water.
- Start the motor and let it idle for about five minutes. This will clean the salt water out of the cooling system.
- Shut off the motor. Remove the motor from the container and keep it in a vertical position until the engine has drained completely. Reinstall the propeller.
- Clean the motor surface and apply a coat of automotive wax on the external finish.
The same pilot-water rule applies here: never operate the motor when there is no water coming out of the pilot water hole, or severe damage can result.
How often to flush
The manual's wording is "after operation in muddy, brackish, or salt water." In South Florida that means after every trip. It is also a step in the storage procedure: the DF2.5 and DF4A/DF6A manuals list it as step 4, "Flush the water passages in the motor thoroughly," before the motor goes away for the season. The full storage list is in how to winterize and store a Suzuki outboard.
Flushing does not replace maintenance. The water pump and thermostat are still inspected and replaced on hours, and a motor used in muddy, silty, sandy, acidic or shallow water may need maintenance more often than the chart shows.
If water does not come out of the pilot hole
Stop. Whether you are on muffs, in a drum or on the water, the instruction is the same in every manual: if no water spray is evident, stop the motor immediately and consult your dealer. On the water, the cooling-water caution system will also cut engine speed; the sequence Suzuki gives for that is in why your outboard is overheating. The usual causes after a flush are muffs that were not sealing, a blocked intake, a worn impeller or a stuck thermostat; the last two are covered in impeller and thermostat replacement.
Parts for this job
You need a set of flush muffs for the engine-running method, and nothing but a garden hose for the flush port if your crate connector is still around. If a flush turns up a weak pilot stream, the water pump repair kits and thermostats are listed by model; use the thermostat part number lookup to pick the right one. We are an authorized Suzuki, Honda and Yamaha dealer, and orders over $149 ship free to the lower 48.
Sources: Suzuki owner's manuals for DF2.5, DF4A/6A, DF8A/9.9A, DF9.9B/15A/20A (2014 and 2020), DF25A/30A, DF40A/50A/60A, DF75/90A, DF100A/115A/140A (2016, 99011-90J70-03B), DF115BG/140BG (2022–2023, 99011-99L20-03B), DF150A/175A/200A (2020; 2023–2024, 99011-96LM0-03B), DF150AP/175AP/200AP, DF225/250, DF250AP/300AP and DF300B/350A (2023, 99011-98L60-03B). Figures are Suzuki's published values; confirm against the manual for your model year and serial number.