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Coolant Temp Alarm Switch 128275-91340 – Fits Yanmar 1GM–3HM
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How to Match This Part
This aftermarket coolant temperature alarm switch replaces Yanmar 128275-91340. It is a 65°C (149°F) switch for the engine alarm circuit on listed Yanmar GM and HM marine diesels with direct raw-water cooling — not a variable sender for a dashboard temperature gauge, and not the 95°C freshwater / heat-exchanger switch used on other GM/HM installations.
Match this part in this order:
1. OEM number on the removed switch or in your parts catalog — Yanmar 128275-91340 (Recmar cross REC128275-91340)
2. Engine model code — on the engine identification plate (typically on the block or flywheel housing)
3. Cooling configuration — this 65°C switch is for direct raw-water cooled applications; freshwater / heat-exchanger cooled GM/HM engines often use a different higher-temperature switch
4. Physical form — threaded metal body with hex wrench flats, white insulated top, and a single stud terminal (compare with the product images)
Do not order from engine family alone. Confirm 128275-91340 (or REC128275-91340), raw-water cooling, and the physical switch against the removed part before installation.
- Primary OEM: 128275-91340
- Type: Coolant temperature alarm switch
- Switch point: 65°C (149°F)
Part Number Cross-Reference
Use these references to confirm interchange. Recmar REC128275-91340 is an aftermarket replacement for Yanmar 128275-91340.
| Type | Brand | Part Number | Notes |
|---|---|---|---|
| OEM | Yanmar | 128275-91340 | Primary SWITCH, 65 reference |
| Aftermarket | Recmar | REC128275-91340 | Aftermarket replacement for 128275-91340 |
Compatible Engine Models
Confirm your Yanmar model on the engine identification plate. Match OEM 128275-91340 and the physical switch form to the product images before purchase. Coverage below is limited to verified model codes for this listing. These applications are for direct raw-water cooled GM/HM engines — freshwater / heat-exchanger installations typically require a different switch.
| Brand | Engine Series | Compatible Model Codes |
|---|---|---|
| Yanmar | 1GM | 1GM, 1GML, 1GMY-C, 1GM10 |
| Yanmar | 2GM | 2GM, 2GMLP, 2GMSZK, 2GM20, 2GM20-YEU |
| Yanmar | 3GM | 3GM30 |
| Yanmar | 3HM | 3HM, 3HM35 |
Technical Specifications
| Specification | Value |
|---|---|
| Part type | Coolant temperature alarm switch |
| Primary OEM | 128275-91340 |
| Switch point | 65°C (149°F) |
| Function | Alarm circuit switch (not a gauge sender) |
| Electrical connection | Single stud terminal |
| Cooling application | Direct raw-water cooled engines |
| Application | Listed Yanmar marine diesel alarm systems calling for 128275-91340 |
Installation Guide
- Allow the engine to cool completely. Isolate battery power before opening the cooling circuit.
- Locate the original temperature alarm switch. Note wire routing and terminal orientation.
- Disconnect the lead, then unscrew the switch using the hex body. Catch residual coolant and keep the port clean.
- Compare the replacement to the original: OEM 128275-91340, 65°C alarm function, white insulated top, and single stud terminal.
- Install using the sealing method and tightening procedure in your Yanmar service manual. Do not apply force to the white insulator. Reconnect the terminal securely.
- Restore coolant as required, restore power, run the engine, and check for leaks plus normal alarm-circuit operation.
Gaskets, sealing washers, sealant, and coolant are not identified as included with this listing. Reuse or renew the original sealing arrangement only as your service manual requires.
Troubleshooting & FAQ
Is this a genuine Yanmar part?
No. This is an aftermarket replacement manufactured to match the OEM-reference fit and function. It is not an OEM or factory Yanmar part.
Is this the alarm switch or the gauge sender?
It is the 65°C temperature alarm switch. It is not the variable sender used to drive an analog temperature gauge.
My catalog shows Recmar REC128275-91340 — is that the same?
Yes. REC128275-91340 is the Recmar aftermarket cross for Yanmar 128275-91340. Still verify raw-water cooling and physical form against the removed switch.
Is this the same as the 95°C Yanmar switch?
No. Yanmar 127610-91350 is a different 95°C switch typically used on freshwater / heat-exchanger cooled applications. This listing is only for 128275-91340 at 65°C.
Does every GM or HM use this switch?
No. Publish coverage is limited to the model codes in the compatibility table that call for 128275-91340 on direct raw-water cooling. Confirm cooling type, OEM number, and physical form; do not order by series name alone.
Why Choose JLM MARINE?
- Precision Fit: Form and function intended for Yanmar 128275-91340 coolant temperature alarm switch applications on the listed marine diesels.
- Quality Control: Each batch is inspected for dimensional consistency and workmanship.
- Direct from Manufacturer: Aftermarket marine sensors engineered as direct replacements — not remanufactured cores.
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