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Starter Motor for Kawasaki STX-12F STX-15F STX 160 | 21163-3721
Starter Motor for Kawasaki STX-12F STX-15F STX 160 | 21163-3721
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Product Overview
Restore reliable starting performance to your Kawasaki personal watercraft with this 12V electric starter motor, designed for compatible STX-12F, STX-15F, and STX 160-series Jet Ski models.
Featuring a 9-tooth drive gear, counterclockwise rotation, 2.7 Nm rated torque, and a 10,500-cycle rating, this starter motor helps provide fast and consistent engine cranking when the original unit becomes weak, slow, intermittent, or unable to start the engine.
The durable metal construction and wear-resistant internal components are designed to withstand repeated starting cycles and demanding marine operating conditions. Its direct-replacement configuration helps simplify installation when the OEM number, mounting diameter, drive gear, terminal position, and overall dimensions match the original starter.
Product Compatibility
| Brand | Model | Model Code / Platform | Year Range | Engine |
|---|---|---|---|---|
| Kawasaki | Jet Ski STX-12F | JT1200B / JT1200D | 2003–2007 | 1199cc |
| Kawasaki | Jet Ski STX-15F | JT1500A | 2004–2019 | 1498cc |
| Kawasaki | Jet Ski STX 160 | JT1500R | 2020–2022 | 1498cc |
| Kawasaki | Jet Ski STX 160X | JT1500S | 2020–2022 | 1498cc |
| Kawasaki | Jet Ski STX 160LX | JT1500T | 2020–2022 | 1498cc |
Kawasaki’s official parts diagrams list 21163-3720 for the 2003 STX-12F and 2004 STX-15F. Later STX-12F and STX-15F diagrams list 21163-3721, including the 2007 STX-12F and 2019 STX-15F. The 2022 STX 160LX also uses 21163-3721.
The STX-15F model name should not be extended through 2022. For 2020–2022 applications, the applicable model names are STX 160, STX 160X, and STX 160LX.
OEM Cross-Reference Numbers
Kawasaki
- 21163-3720
- 211633720
- 21163-3721
- 211633721
Common Aftermarket Cross References
- Lester/WAI: 18432
- Lester/WAI: 18432N
- SBT: 503SB213
Kawasaki OEM number 21163-3721 supersedes or replaces the earlier 21163-3720 starter number.
Your original starter does not need to display every number listed above. However, at least one compatible OEM or interchange number should match the original unit or the official parts catalog for your watercraft.
Specifications
| Specification | Details |
| Product Type | Electric Starter Motor |
| Voltage | 12V |
| Drive Gear | 9 Teeth |
| Rotation | CCW / Counterclockwise |
| Rated Torque | 2.7 Nm |
| Cycle Rating | 10,500 Cycles |
| Overall Length | 189 mm / 7.44 in |
| Mounting / Insertion Diameter | 45 mm / 1.77 in |
| Fitment Type | Direct Replacement |
| Vehicle Type | Personal Watercraft / Jet Ski |
| Housing Material | Metal |
| Condition | New |
| Package Quantity | 1 Starter Motor |
Rotation descriptions may vary depending on which end of the starter is viewed. Confirm compatibility using the OEM number, tooth count, drive-end shape, mounting diameter, terminal position, overall dimensions, and product photos.
Measurements may vary slightly depending on the measuring method. Compare the same measurement points shown in the product images with your original starter.
Key Features
- Broad Kawasaki PWC Fitment: Designed for compatible STX-12F, STX-15F, and STX 160-series personal watercraft.
- 12V 9-Tooth Configuration: Features a 9-tooth drive gear and counterclockwise rotation for compatible Kawasaki starting systems.
- Strong Cranking Performance: Rated at 2.7 Nm to help provide fast and consistent engine startup.
- Durable Construction: Wear-resistant internal components help support dependable operation under demanding marine conditions.
- Direct-Replacement Design: Matches the original-style mounting and electrical configuration when all specifications are correct.
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Fitment FAQ
Will this part fit my specific model and year?
This starter motor is designed for compatible:
2003–2007 Kawasaki Jet Ski STX-12F JT1200
2004–2019 Kawasaki Jet Ski STX-15F JT1500
2020–2022 Kawasaki Jet Ski STX 160 JT1500
2020–2022 Kawasaki Jet Ski STX 160X JT1500
2020–2022 Kawasaki Jet Ski STX 160LX JT1500
Your original starter should use OEM 21163-3720 or 21163-3721 and match the listed 12V, 9-tooth configuration, mounting diameter, terminal position, and overall dimensions.
Do not identify a 2020–2022 model as an STX-15F without checking the complete model name. Those model years are generally part of the STX 160 family.
Do I need to match the OEM part number?
Yes. Matching the complete OEM number is one of the most reliable ways to confirm compatibility.
This starter motor replaces:
21163-3720
211633720
21163-3721
211633721
Lester 18432
Lester 18432N
SBT 503SB213
The original starter does not need to display every number listed above. At least one compatible OEM or cross-reference number should match your original unit or the official parts catalog.
OEM 21163-3721 is the later replacement for 21163-3720, so either Kawasaki number may appear in the application history.
What models or situations does this part not fit?
This starter motor is not intended for:
Kawasaki personal watercraft using a different OEM starter number
Two-stroke STX models that do not use 21163-3720 or 21163-3721
Kawasaki 750, 900, 1100, or other engine platforms using different starters
Applications requiring a different number of drive teeth
Starters with a different mounting or insertion diameter
Models with a different electrical terminal position
Watercraft with engine swaps or modified starting systems
Applications where the original starter has a different housing or drive-end shape
Do not assume that every Kawasaki STX or JT1500 model uses the same starter motor.
What should I check before ordering?
Before ordering, confirm:
Watercraft brand and complete model name
Exact production year
Complete JT model code
Hull identification number when needed
OEM or interchange part number
12V operating voltage
9-tooth drive gear
Counterclockwise rotation using the same viewing convention
189 mm / 7.44 in overall length
45 mm / 1.77 in mounting or insertion diameter
Electrical terminal location
Mounting-point positions
Starter housing and drive-end shape
Condition of the O-rings and sealing surfaces
Also test the battery, starter relay, fuse, cables, wiring, and ground connections. Corroded electrical connections or a weak marine battery can create symptoms similar to a failed starter motor.