A Suzuki electric-start outboard wants a 12 V starting-type (cranking) lead-acid battery that meets the minimum in the manual, connected positive first, with hex nuts on the posts, through cable no lighter than the gauge Suzuki gives for your family: heavier than AWG 8 on the portables, heavier than AWG 5 on the DF40A to DF60A, heavier than AWG 4 on the DF70A to DF140B, and heavier than AWG 2 from the DF150A up. From the DF100A/115A/140A upward there is also a sub-battery cable with its own fuse that feeds the engine control system; wire it wrong and the motor will not start, or the fuse blows.
The MCA/CCA/RC minimums per model are on the battery requirements chart; this page covers everything else, from Suzuki's set-up (installation) and owner's manuals.
Which battery: cranking type, not deep cycle
Every Suzuki manual agrees on battery type. The older wording (DF8A/9.9A 2014, DF9.9B/15A/20A 2014, and the DF70A/90A and DF115A/140A set-up manuals) is: choose a 12 volt cranking-type lead acid battery; do not use a deep cycle battery for the main cranking battery; maintenance-free, sealed or gel-cell batteries are not recommended because they may not be compatible with Suzuki's charging system. Dual-purpose (cranking/deep cycle) batteries can be used if they meet the minimum specifications (MCA, CCA or RC).
The newer wording (DF40A/50A/60A 2022, DF225/250 2022, DF250AP/300AP and DF300B/350A owner's manuals, and the DF40A to DF60A, DF115B/140B and DF150A-and-up set-up manuals) is shorter: do not use deep cycle batteries and gel-cell batteries for starting engines; use a 12 volt starting-type lead acid battery that meets the specifications. The 2020 DF9.9B/15A/20A manual keeps the deep-cycle line but no longer prints the sealed/gel-cell note. Either way, the ratings in the manual are minimums for starting. If the boat carries extra electrical loads, the DF40A/50A/60A manual recommends installing an auxiliary battery or batteries; on a recoil-start DF9.9B/15A/20A the manual says running accessories needs a 35 AH or larger battery, a rectifier and related items, and on a recoil-start DF25A/30A a 70 AH or larger battery.
- Batteries in parallel: same type, capacity, manufacturer and similar age, replaced as a set.
- Twin or multiple engines: one battery per engine.
- Store the battery away from splashing water and fix it securely to the hull with a battery band or similar; the DF8A/9.9A set-up manual recommends an enclosed battery box.
Battery cable size by family
None of the manuals gives a gauge-by-length table. Each states one minimum for any extension of the supplied battery cable, and "larger" means a thicker cable, which is a lower AWG number (the DF250AP/300AP manual spells this out: AWG number 2 or larger thickness, lower gauge number).
| Family (set-up manual) | Minimum when extending the battery cable | Notes from the same manual |
|---|---|---|
| DF8A/DF9.9A (99505-99J00-01E, 2010) | Larger than AWG 8 equivalent (AV8) | Connect + first, then −; hex nuts; enclosed battery box recommended |
| DF9.9B/DF15A/DF20A (99505-89L10-01E, 2013) | Larger than AWG 8 | T models: do not connect the sub-battery cable to the remote harness (it blows the sub-battery fuse) |
| DF25A/DF30A (99505-94L10-01E, 2014) | Larger than AWG 8 | Same sub-battery cable notice |
| DF40A/DF50A/DF60A (99505-88L40-01E, 2022) | Larger than AV15 (AWG 5) | Connect positive first; hex nuts; one battery per engine on twins |
| DF70A/DF80A/DF90A/DF100B (99505-87L50-01E, 2020) | Larger than AV20 (AWG 4) | Do not connect a sub-battery cable on this family; the sub-battery fuse will blow |
| DF115A/DF140A (99505-92J20-01E, 2015) | Larger than AV20 (AWG 4) | Sub-battery cable 3.7 m (36625-93J00) with 15 A fuse must be connected to the positive terminal |
| DF100C/DF115B/DF140B (99505-99L40-01E, 2022) | Larger than AV20 (AWG 4) | Sub-battery cable 3.7 m (36625-93J0*) with 15 A fuse, positive terminal |
| DF150A/DF175A/DF200A (99505-96L60-01E, 2022) | Larger than AV30 (AWG 2) | Negative-to-negative link between engine and accessory batteries: AWG 2 (6.543 mm) or larger |
| DF150AP/DF175AP/DF200AP (99505-96L70-01E, 2022) | Larger than AV30 (AWG 2) | Sub-battery cable connects to both + and −; do not cut or extend the harness |
| DF250AP/DF300AP (99505-98J40-01E, 2021) | Larger than AWG 2 | Negatives linked with AWG 2 or larger; the sub-battery cable must be correctly connected or the engine cannot start |
| DF300B/DF350A (99505-98L40-01E, 2022) | Larger than AWG 2 | Same as DF250AP/300AP |
Connection order and terminal hardware
- Connect the red lead from the motor to the positive battery terminal first. On models with a sub-battery cable, connect the positive battery cable and the sub-battery cable to the positive terminal together in this step.
- Then connect the black lead to the negative terminal. On the DF150AP/175AP/200AP the battery cable and sub-battery cable go to both the positive and negative terminals.
- To remove a battery, disconnect the black (negative) lead first, then the red. On AP models the set-up manual adds: turn the main switch OFF before disconnecting, and when reconnecting turn the main switch OFF, positive first, then negative.
- Use hexagon nuts to secure the cables to the posts, to avoid loss of electrical power. Do not use wing nuts.
- Suzuki recommends a terminal cap on the positive terminal to prevent an accidental short.
- Never disconnect battery leads while the engine is running.
- If you run an electric-start model without a battery, insulate the terminal ends of the battery cables so they cannot touch.
If the battery is not maintenance-free, the manuals say to check the fluid level every 100 hours or 12 months. Suzuki also asks for antennae at least one meter (40 inches) from the engine cowling.
Second battery and the isolator
From the DF150A up, the motor's charging system has an isolator function built in. The set-up manuals describe the conversion in three moves: install the optional battery isolator lead set, relocate one fuse in the fuse box from its STD position to OPT, and fit the terminal cover on the vacated STD position. The manuals also size the accessory battery and cap the charge through the isolator lead.
| Family | Fuse to relocate | Isolator lead set | Accessory battery (or larger) | Charge through isolator lead |
|---|---|---|---|---|
| DF150A/DF175A/DF200A | 30 A, STD to OPT | 33830-98J1* | 850 MCA, or 650 CCA, or 180 RC, or 12 V 100 AH (as printed; the starting battery row in the same manual says 670 CCA) | Max 25 A per motor; 50 A or 75 A total for twins or triples on a common auxiliary battery |
| DF150AP/DF175AP/DF200AP | 30 A, STD to OPT | 33830-98J1* | 850 MCA, or 670 CCA, or 180 RC, or 12 V 100 AH | Max 25 A per motor; 50 A or 75 A total |
| DF250AP/DF300AP | 40 A, STD to OPT | 33830-98J11 | 1000 MCA, or 800 CCA, or 180 RC, or 12 V 130 AH | The manual prints the 25 A note worded for the DF300B/325A/350A |
| DF300B/DF350A | 40 A, STD to OPT | 33830-98J1* | 1000 MCA, or 800 CCA, or 180 RC, or 12 V 130 AH | Max 25 A per motor; 50 A or 75 A total |
Connect the negative terminal of the engine battery to the negative terminal of the accessory battery with AWG 2 cable. If the second battery stops charging, the owner's manuals say to check whether the fuse in the OPT position is blown (30 A on the DF150A/AP families, 40 A on the DF250AP/300AP), and to replace it only with the same type and rating. All fuse ratings are on the fuse chart.
The sub-battery cable and the fuse that blows if you wire it wrong
On the DF100A/115A/140A, DF100C/115B/140B, DF150A to DF200A, DF225/250, the AP models and the DF300B/350A, a thinner second cable runs from the battery to the motor. The DF250AP/300AP manual: the sub-battery cable is used to supply voltage to the engine control system. In the middle of the cable is a fuse, 15 A on the DF100A/115A/140A, DF115B/140B, DF150A/175A/200A and DF225/250, and 30 A on the DF150AP/175AP/200AP, DF250AP/300AP and DF300B/350A. If the sub-battery cable is not correctly connected to the battery, the engine cannot start. The set-up manuals tell the installer to put this fuse somewhere the operator can see it.
Two things to get right.
- On the DF115A/140A, DF115B/140B and non-AP DF150A/175A/200A it goes to the positive terminal, with the positive battery cable. On the DF150AP/175AP/200AP it connects to both the positive and negative terminals, and on multi-engine AP and DF300B/350A installs the manuals say all negative battery terminals should be connected together to keep the BCM powered. Follow the set-up manual diagram for the DF250AP/300AP and DF300B/350A.
- On the DF70A/80A/90A/100B there is no sub-battery cable to connect. The set-up manual says it is not necessary to connect one to power the engine control system, and if you connect the sub-battery cable, the sub-battery fuse will blow. The DF9.9B/15A/20A power-tilt (T) and DF25A/30A set-up manuals carry a similar notice: do not connect the sub-battery cable to the remote-control harness or it blows the sub-battery fuse.
If a motor with a sub-battery cable will not start with a good main battery, the DF150AP/175AP/200AP and DF250AP/300AP owner's manuals list the sub-battery cable fuse right after the starter relay fuse under "starter motor will not operate". Check it right after the lanyard plate.
Drive-by-wire (AP) models: extra rules
The Suzuki Precision Control (AP) set-up manual adds electrical precautions that do not apply to mechanical-control motors. Do not cut or extend the wiring harness and lead wires; water can enter at the joint and cause a continuity error that shows up as shifting and throttle control errors. Ensure all connections are correct and tight and plug unused connectors with a waterproof cap. Install the BCM with its connector facing downward, in a place that does not exceed 75 °C (167 °F), and keep navigation and radio equipment more than 50 cm (20 in) from the BCM and the motor. If the BCM and ECM are an improper combination the engine will not start: the buzzer sounds, the gauge shows "Check Control Unit C" and cranking does not take place. After installation the system requires electronic calibration by someone specifically trained on Suzuki Precision Control, so that step is dealer work; check with your dealer if the motor is under warranty.
Parts for this job
Battery cables, sub-battery cables and remote harnesses are in Suzuki OEM wiring harnesses and cables; isolator lead sets, rectifier/regulators and starter relays under starters and charging systems; fuses and holders under fuses, bulbs and electrical accessories; ignition switches and key panels under switches and keys. For the small motors we sell complete, see the notes on batteries for 9.9, 15 and 20 hp and batteries for 25 and 30 hp. Free shipping on orders over $149 to the lower 48.
Sources: Suzuki set-up manuals 99505-88L40-01E, 99505-87L50-01E, 99505-92J20-01E, 99505-99L40-01E, 99505-96L60-01E, 99505-96L70-01E, 99505-98J40-01E, 99505-98L40-01E and the DF8A/9.9A, DF9.9B/15A/20A and DF25A/30A set-up manuals; Suzuki owner's manuals for DF8A/9.9A (2014), DF9.9B/15A/20A (2014 and 2020), DF25A/30A (2019), DF40A/50A/60A (2022), DF75/DF90A (2023), DF100A/115A/140A (2016), DF115B/140B (2023), DF150A/175A/200A (2020), DF150AP/175AP/200AP (2020), DF225/250 (2022), DF250AP/300AP (2022), DF300B/350A (2023). Figures are Suzuki's published values; confirm against the manual for your model year and serial number.