OEM Outboard Motor Thermostats

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The thermostat regulates cooling-water flow so the outboard reaches and holds its operating temperature. One that sticks closed overheats the engine within minutes; one that sticks open keeps it too cold, which raises fuel consumption and wear and can foul plugs. Each brand, and often each engine family within a brand, uses its own thermostat and opening temperature, so they are not interchangeable.

Boat Max Online stocks genuine OEM thermostats for Honda BF, Suzuki DF and Yamaha F series outboards. Use the brand collections for the exact part: Suzuki thermostats, Yamaha thermostats, and Honda thermostats under Honda Marine parts.

Suzuki thermostat part numbers and opening temperatures

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

Suzuki's schedule is to inspect the thermostat every 100 hours or 12 months and replace it when it fails inspection; the owner's manuals do not set a fixed replacement age. For Honda and Yamaha, use the interval and opening temperature in that engine's owner's manual.

Authorized dealer for Honda, Suzuki and Yamaha; every thermostat is a genuine OEM part. Free shipping on orders over $149 to the lower 48 states.

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