Suzuki's current schedules have the water pump inspected at 200 hours (12 months) and the impeller replaced every 300 hours (36 months); the thermostat is inspected every 100 hours (12 months). The impeller lives in the lower unit, so the job is: drop the gearcase, unbolt the pump case, fit the new impeller and gaskets, refit the case while turning the driveshaft clockwise, torque the case and gearcase bolts, and check for water at the pilot hole. The thermostat is in the cylinder block under a small cover and is tested by heating it in water.
Know this first: the owner's manuals mark the water pump, impeller and thermostat with an asterisk, meaning Suzuki recommends that only an authorized Suzuki marine dealer or a qualified service mechanic perform them. The steps below are the service manual's, for the families where our copy includes them. If the motor is under warranty, check with your dealer before doing this yourself.
When to replace the impeller and thermostat
| Family | Inspect water pump / impeller | Replace impeller | Inspect thermostat | Note |
|---|---|---|---|---|
| DF2.5 | 200 h | 300 h (36 months) | 100 h | Later service manual schedule (also the 2019 owner's manual); thermostat was added as a service item in that revision |
| DF4A/DF6A | 200 h | 300 h (36 months) | 100 h | 2020 owner's manual chart; the older DF4/DF5/DF6 service manual says replace every 200 h (12 months) |
| DF8A/DF9.9A | 200 h | 300 h (36 months) | 100 h | 2014 owner's manual chart; the service manual says replace every 200 h (12 months) |
| DF9.9B/DF15A/DF20A | 200 h (12 months) | 300 h (36 months) | 100 h (12 months) | Service manual states both intervals in words |
| DF25A/DF30A | 200 h (12 months) | 300 h (36 months) | 100 h (12 months) | Service manual |
| DF40A/DF50A/DF60A | 200 h | 300 h (36 months) | 100 h | 2022 owner's manual chart; the 2010-based DF60 service manual says replace every 200 h (12 months) |
| DF70A/DF80A/DF90A/DF100B | 200 h (12 months) | 300 h (36 months) | 100 h (12 months) | Service manual |
| DF100A/DF115A/DF140A | 200 h (12 months) | 300 h (36 months) | 100 h | Service manual and 2016 owner's manual agree |
| DF115B/DF140B, DF115BG/DF140BG | 200 h | 300 h (36 months) | 100 h | 2023 DF115B/140B owner's manual chart; the 2022–2023 DF115BG/140BG owner's manual prints the same marks (water pump I at 200 h, impeller I at 200 h and R at 300 h, thermostat I at 100 h) |
| DF150A/DF175A/DF200A | 200 h | 300 h (36 months) | 100 h | 2023 owner's manual chart (DF150A/AZ, DF175A/AZ, DF200A/AS/AZ); no service manual in our set, so intervals only |
| DF300B/DF350A | 200 h | 300 h (36 months) | 100 h | 2023 owner's manual chart (DF300B/BMD, DF350A/AMD); no service manual in our set, so intervals only |
Hours or months, whichever comes first. Replace sooner on the warning signs in our impeller interval guide: a weak or missing pilot stream, or the overheat caution. The manual's rule: never operate the motor when there is no water coming out of the pilot water hole, or severe damage can result. With the impeller out, replace it if the vanes are cut, torn or worn; replace the pump case if cracked or distorted, and the inner sleeve or under panel if worn, cracked, distorted or corroded.
Tools and parts
- A water pump repair kit for your model. The manuals discard the plate gasket, and on the DF70A–DF100B the pump-case seal ring is never reused; the impeller key is kept for reuse.
- The thermostat for your family (table below) from our thermostat part number lookup, with its cover seal or gasket.
- Suzuki water resistant grease, Suzuki silicone seal, Suzuki Bond 1207B where called for, Thread Lock on the DF4/DF5/DF6 pump nuts, and a torque wrench that reads down to 5–6 N·m.
- Gear oil if you drain the lower unit (the DF2.5 and DF4/DF5/DF6 procedures do): see gear oil capacities.
Never turn the engine backwards. Every service manual repeats it: rotate the crankshaft in the normal running direction only (clockwise) to prevent water pump impeller damage. On electric-start motors, disconnect the battery cable before removing the lower unit.
Impeller replacement, by family
The job in outline
- Disconnect the battery cable (electric start) or the spark plug cap (DF2.5); separate the shift linkage as your manual describes.
- Remove the gearcase bolts and lower the gearcase off the driveshaft housing.
- Remove the pump case fasteners and case; lift off the impeller, key, under plate and dowel pins.
- Fit new gaskets and the new impeller (key in the keyway), refit the case while rotating the driveshaft clockwise so the vanes bend the right way, and torque the case fasteners.
- Refit the gearcase with grease on the driveshaft splines and silicone seal on the mating surfaces and bolts, water tube seated in the pump outlet; torque the gearcase bolts and reconnect the shift linkage.
DF9.9B, DF15A, DF20A (service manual 99500-89L00-01E)
- Disconnect the battery cable. Loosen the clutch rod lock nut, then unscrew the connector to separate the clutch rod from the shift rod (the manual warns the clutch rod connector is not a turnbuckle). Remove the four gearcase bolts and separate the gearcase.
- Loosen the four nuts and remove the water pump case.
- Remove the impeller, impeller key, pump under plate and dowel pins. Keep the key for reuse and discard the plate gasket.
- Remove the inner sleeve from the pump case; the manual suggests warming the case with a hair dryer to ease it out. Inspect and replace as described above.
- Install: place the dowel pins, under panel gasket and under panel; install the pump case gasket; insert the key in the driveshaft and slide the impeller on with key and keyway aligned.
- Install the inner sleeve into the pump case, aligning its projection with the groove. Apply Suzuki Bond 1207B lightly between sleeve and case, but not on the top of the sleeve; put a light coat of water resistant grease on the sleeve and under panel for initial lubrication.
- Install the pump case assembly while rotating the driveshaft clockwise to flex the vanes in the correct direction. Tighten the four pump case nuts to 6 N·m (0.6 kgf-m, 4.3 lbf-ft).
- Refit the lower unit: apply water resistant grease to the driveshaft splines and a light coat of Suzuki silicone seal to the mating surfaces; slide the lower unit into place so the driveshaft engages the crankshaft and the water tube locates in the pump; apply silicone seal to the retaining bolts and tighten the gearcase bolts to 17 N·m (1.7 kgf-m, 12.3 lbf-ft). Reconnect the clutch rod.
DF70A, DF75, DF80A, DF90A, DF100B (service manual 99500-87L10-01E)
- Disconnect the battery cable. Remove the five gearcase bolts and separate the gearcase; disconnect the speedometer pick-up tube before the gearcase is fully off.
- Loosen the four bolts and remove the water pump case.
- Remove the impeller, impeller key and pump under plate; keep the key for reuse and discard the plate gasket.
- Remove the inner sleeve and the rubber seal ring (warm the case with a hair dryer to ease the sleeve out). Do not reuse the seal ring once removed.
- Install: dowel pins, under panel gasket and under panel; insert the key in the driveshaft and slide the impeller on with key and keyway aligned.
- Place a new seal ring into the groove of the pump case, fit the inner sleeve with its projection in the groove, and apply water resistant grease lightly on the pump sleeve and under panel.
- Install the pump case assembly while rotating the driveshaft clockwise to flex the vanes in the correct direction. Tighten the four pump case bolts to 17 N·m (1.7 kgf-m, 12.3 lbf-ft).
- Before installing the lower unit, bring the shift rod to neutral. Apply water resistant grease to the driveshaft and shift rod splines, silicone seal to the five gearcase bolts, and tighten them to 55 N·m (5.5 kgf-m, 40.0 lbf-ft).
DF2.5 (service manual 99500-97J01-01E)
- Disconnect the spark plug cap before removing the lower unit. With the shift linkage separated as the manual shows, remove the two bolts and separate the gearcase from the driveshaft housing.
- Drain the gear oil (the manual removes the drain plug before the level plug). Pull out the shift rod, remove the four bolts and the pump case, then the impeller, key and pump under panel.
- Install: apply Suzuki Bond 1207B to both sides of the under panel gasket, evenly; fit the under panel, the impeller pin and the impeller. A later supplement adds: before installing the impeller, apply water resistant grease to its inner surface so it will not stick to the driveshaft.
- Apply Bond 1207B to the outer surface of the pump sleeve and fit it into the pump case with the boss in the groove.
- Install the pump case while rotating the driveshaft clockwise; tighten the pump case bolts to 5 N·m (0.5 kg-m, 3.5 lb-ft).
- The manual then pressure-tests the gearcase: a low initial 20–40 kPa, then 100 kPa (1.0 kg/cm², 14.2 psi) held for at least 5 minutes, never above 110 kPa (1.1 kg/cm², 15.6 psi) or the oil seals are damaged.
- Apply silicone seal to the gearcase retaining bolts and tighten to 8 N·m (0.8 kg-m, 6.0 lb-ft). Refill the gear oil.
DF4, DF5, DF6 (service manual 99500-91J03-01E)
This is the manual for the DF4/DF5/DF6; the DF4A/DF6A owner's manual we have gives no pump procedure, so treat these as the closest published steps and confirm against your own manual.
- Drain the gear oil (drain plug out before the level plug). Remove the clutch adjust hole cover and loosen the rod connecting plate bolt approximately one turn; do not over-loosen it.
- Remove the two nuts and washers (L transom) or two bolts (S transom) and separate the gearcase.
- Remove the four nuts and washers, the water pump case, then the impeller, key, dowel pin and pump under panel.
- Install the under panel, dowel pin, key and impeller; install the pump case while rotating the driveshaft clockwise. Apply Thread Lock to the pump case nuts and tighten to 8 N·m (0.8 kg-m, 6.0 lb-ft).
- Refit the gearcase with silicone seal on the retaining nuts (bolts on the S model) at 17 N·m (1.7 kg-m, 12.5 lb-ft), making sure the water tube passes through the guide plate hole into the pump outlet and the shift rod passes through the rod connecting plate. Refill with 190 ml (6.4/6.7 US/Imp oz) of gear oil and set the rod connecting plate bolt to 11 N·m (1.1 kg-m, 8.0 lb-ft).
Families where our service manual is truncated
Our copies of the DF8A/DF9.9A, DF25A/DF30A, DF40A/DF50A/DF60A and DF100A/DF115A/DF140A service manuals stop before the water pump section, so the procedure for those families is not covered here. They do give the intervals above, the same clockwise-only rule, and the fastener torques:
| Family | Water pump case | Gearcase bolts | Thermostat cover |
|---|---|---|---|
| DF2.5 | Bolt 5 N·m (0.5 kg-m, 3.5 lb-ft) | 8 N·m (0.8 kg-m, 6.0 lb-ft) | Not stated (four bolts; sealant on both faces of the gasket) |
| DF4/DF5/DF6 | Nut 8 N·m (0.8 kg-m, 6.0 lb-ft), with Thread Lock | 17 N·m (1.7 kg-m, 12.5 lb-ft) | Intake manifold bolts 10 N·m (1.0 kg-m, 7.0 lb-ft) |
| DF8A/DF9.9A | Nut 6 N·m (0.6 kgf-m, 4.3 lbf-ft) | 17 N·m (1.7 kgf-m, 12.3 lbf-ft) | 23 N·m (2.3 kgf-m, 16.5 lbf-ft) |
| DF9.9B/DF15A/DF20A | Nut 6 N·m (0.6 kgf-m, 4.3 lbf-ft) | 17 N·m (1.7 kgf-m, 12.3 lbf-ft) | 10 N·m (1.0 kgf-m, 7.2 lbf-ft) |
| DF25A/DF30A | Nut 6 N·m (0.6 kgf-m, 4.3 lbf-ft) | 23 N·m (2.3 kgf-m, 16.5 lbf-ft) | 11 N·m (1.1 kgf-m, 8.0 lbf-ft) |
| DF40A/DF50A/DF60A | Nut 8 N·m (0.8 kgf-m, 5.8 lbf-ft) | 23 N·m (2.3 kgf-m, 16.6 lbf-ft) | 10 N·m (1.0 kgf-m, 7.2 lbf-ft) |
| DF70A/DF80A/DF90A/DF100B | Bolt 17 N·m (1.7 kgf-m, 12.3 lbf-ft) | 55 N·m (5.5 kgf-m, 40.0 lbf-ft) | 10 N·m (1.0 kgf-m, 7.0 lbf-ft; 7.2 in the procedure page) |
| DF100A/DF115A/DF140A | Bolt 17 N·m (1.7 kgf-m, 12.5 lbf-ft) | 54 N·m (5.5 kgf-m, 40.0 lbf-ft) | 10 N·m (1.0 kgf-m, 7.0 lbf-ft) |
Thermostat replacement
Opening temperature by family
| Family | Thermostat opening temperature (service manual) |
|---|---|
| DF2.5 | 48–52 °C (118–126 °F) |
| DF4/DF5/DF6 | 48–52 °C (118–126 °F); from serial 110001, DF4 48–52 °C and DF5/DF6 40–44 °C (104–111 °F) |
| DF8A/DF9.9A | 58–62 °C (136–144 °F) |
| DF9.9B/DF15A/DF20A | 48–52 °C (118–126 °F) |
| DF25A/DF30A | 58–62 °C (136–144 °F) |
| DF40A/DF50A/DF60A | 58–62 °C (136–144 °F) |
| DF70A/DF80A/DF90A/DF100B | 58–62 °C (136–144 °F) |
| DF100A/DF115A/DF140A | 48–52 °C (118–125 °F) |
Larger motors are not in the service manuals we hold; use the thermostat lookup for those.
Testing the old thermostat
Every service manual we have uses the same test. If salt deposits, corrosion, wear or other damage is found, clean or replace it. Insert a length of thread between the thermostat valve and body, suspend it in a container of water, put a thermometer in the water and heat it; watch the temperature at which the valve opens and releases the thread. If it does not open within the range for your family, or sticks in any position, replace it.
DF9.9B, DF15A, DF20A
- Remove the recoil starter. Disconnect the breather hose from the silencer case; remove the bolt and the silencer case.
- Disconnect the IAC valve connector and the MAP sensor connector; remove the bolt securing the anode cover.
- Remove the three bolts securing the thermostat cover, then the cover and thermostat.
- Install the seal to the thermostat cover. Install the thermostat with its air leak hole facing upward toward the top of the engine.
- Fit the cover and tighten the thermostat cover bolts to 10 N·m (1.0 kgf-m, 7.2 lbf-ft); refit the anode cover bolt, connectors, silencer case and recoil starter.
DF70A, DF75, DF80A, DF90A, DF100B
- Remove the ring gear cover. Loosen the clip and remove the water return hose from the thermostat cover.
- Remove the two bolts securing the thermostat cover and lift off the cover with the thermostat; remove the thermostat and cover seal.
- Assemble the thermostat, seal and cover, install, and tighten the cover bolts to 10 N·m (1.0 kgf-m, 7.2 lbf-ft).
DF2.5
Remove the recoil starter, then the four bolts and the thermostat cover, and take out the thermostat. On US-market engines covered by the later supplement, the cover is behind the fuel pump: remove the two fuel pump bolts and the pump, the two bracket bolts, then the two thermostat cover bolts and the cover. On installation, apply sealant to both faces of the thermostat cover gasket (the hatched areas in the manual), then fit the gasket and cover to the cylinder block.
DF4, DF5, DF6
The thermostat sits under the intake manifold: remove the four bolts, the manifold and its gasket, and take out the thermostat. Install the thermostat, then the manifold with a new gasket, tightening the four bolts diagonally to 10 N·m (1.0 kg-m, 7.0 lb-ft).
Other families
The thermostat pages for the DF8A/DF9.9A, DF25A/DF30A, DF40A/DF50A/DF60A and DF100A/DF115A/DF140A are not in our copies of those manuals; only the cover-bolt torques and opening temperatures above are. The DF60 manual's contents also list a water pressure valve on that family.
Testing afterwards
Put the motor in water or on muffs (see how to flush a Suzuki), shift to neutral with the propeller removed, and start it. As soon as the engine starts, water should spray out of the pilot water hole; if no spray is evident, stop the motor immediately. On muffs, run only at idle. If the overheat caution lights later, the manual's first steps are to reduce speed and check the pilot hole; our overheating guide takes it from there. On a lower unit you have had apart, watch the gear oil at the next change: milky oil is contaminated with water, and the manual says not to operate the motor until the oil is changed and the cause corrected.
Parts for this job
Boat Max Online is an authorized Suzuki, Honda and Yamaha Marine dealer with free shipping on orders over $149 to the lower 48. Find your water pump kit and impeller (the DF4/DF6 and DF4A/DF6A kit is listed separately), the right Suzuki thermostat, and ECSTAR gear oil for the refill.
Sources: Suzuki owner's manuals for DF2.5, DF4A/DF6A, DF8A/DF9.9A, DF9.9B/DF15A/DF20A, DF40A/DF50A/DF60A, DF100A/DF115A/DF140A (99011-90J70-03B), DF115B/DF140B, DF115BG/DF140BG (99011-99L20-03B), DF150A/DF175A/DF200A (99011-96LM0-03B) and DF300B/DF350A (99011-98L60-03B); Suzuki service manuals 99500-97J01-01E (DF2.5), 99500-91J03-01E (DF4/DF5/DF6), 99500-99J00 (DF8A/DF9.9A), 99500-89L00-01E (DF9.9B/DF15A/DF20A), 99500-94L10-01E (DF25A/DF30A), 99500-88L01-01E (DF60), 99500-87L10-01E (DF70A/DF80A/DF90A/DF100B) and 99500-92J00-01E (DF100A/DF115A/DF140A). Figures are Suzuki's published values; confirm against the manual for your model year and serial number.