Suzuki Outboard Thermostats | Boat Max Online for Sale

The thermostat is one of the most critical and most overlooked parts of a Suzuki outboard's cooling system. It controls cooling-water flow so the engine warms up quickly and holds a steady temperature. A thermostat that sticks closed can overheat the engine in a few minutes; one that sticks open keeps it too cold, which raises fuel consumption, accelerates wear and can foul spark plugs. EFI models from the DF9.9B up also have a Check Thermostat alert that stays on until the ECM sees normal warm-up again, so replacing the part alone does not clear it.

Suzuki's maintenance schedule is to inspect the thermostat every 100 hours or 12 months and replace it if it fails inspection. Genuine Suzuki thermostats are calibrated to the opening temperature for each engine family, and the families do not share one temperature:

Suzuki model	Thermostat P/N	Opening temperature
DF2.5, DF4A/5A/6A, DF9.9B/15A/20A	17670-91J02	48–52 °C (118–126 °F)
DF8A/9.9A, DF25 V-twin, DF25A/30A	17670-94J02	58–62 °C (136–144 °F)
DF40A/50A/60A, DF50AV/60AV	17670-93955	58–62 °C
DF70A/80A/90A/100B, DF90/100/115/140 (2001–2012)	17670-90J01	58–62 °C
DF100A/115A/140A (2013+)	17670-90J21	48–52 °C
DF100C/115B/140B, DF115BG/140BG	17670-90J01	58–62 °C
DF150/175 (2006+)	17670-90J21	58–62 °C
DF150TG/175TG, DF150A/175A, DF150AP/175AP, DF200A/AP	17670-90J21	48–52 °C
DF200/225/250 V6, DF300 (2007–2011)	17670-90J01	58–62 °C
DF250AP/300AP	17670-90J21	48–52 °C
DF300B/325A (2020+), DF350A (2019+)	17670-98L20	58–62 °C
DF350A (2018)	17670-98L00	53–57 °C

Boat Max Online stocks OEM Suzuki thermostats and thermostat gaskets for the DF lineup. Order by model and year.

Authorized Suzuki Marine dealer. Free shipping on orders over $149 to the lower 48 states.

Source: Suzuki 4-Stroke Outboard Maintenance Manual, Service Data (Feb 2025).

Suzuki Thermostats