Genuine Tohatsu Standard Piston 309-00001-1 2.5/3.5HP 2-Stroke
309-00001-1
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Tohatsu Standard Piston
Genuine 309-00001-1 | Standard bore size
Genuine Tohatsu standard-size piston for specified 2.5HP and 3.5HP two-stroke powerheads. It is intended for a serviceable standard bore; it is not the 0.5mm oversize piston used after cylinder re-machining.
Key Features
- ✔ Genuine Tohatsu OEM piston
- ✔ Standard-size specification
- ✔ For selected 2.5/3.5HP two-stroke powerheads
- ✔ Exact part number 309-00001-1
- ✔ Piston only unless additional components are shown
Technical Specs
| Part type | Piston |
| Size | Standard / STD |
| Engine cycle | 2-stroke |
| Power family | 2.5HP / 3.5HP |
| Manufacturer number | 309-00001-1 |
| 4Boats SKU | 309-00001-1 |
Compatibility / Fitment Guide
Verified base engine family: Tohatsu M2.5A2, M3.5A2 and M3.5B2 and Nissan Marine NS2.5A2, NS3.5A2 and NS3.5B2 two-stroke outboards, only where the serial-specific piston/crankshaft diagram lists the exact part number in this listing.
Bore condition: use only with a standard-dimension cylinder that remains within the factory wear, taper and out-of-round limits. Confirm piston-to-cylinder clearance after measurement.
Identification rule: read the model and serial plate, then check the correct internal-engine diagram. Similar-looking 309, 3F0, 302, 361 and other numbered parts are not interchangeable by appearance.
Exclusions: not for M5, M6, M8 or M9.8; not for MFS four-strokes; and not for a cylinder machined for a 0.5mm oversize piston.
Part Number Cross Reference
| Tohatsu current | 309-00001-1 |
| Earlier/catalogue format | 309-00001-0 / 309000010M |
| Standard ring reference | 302-00011-0 (verify separately) |
| 4Boats SKU | 309-00001-1 |
Piston rings, pin and clips are separate catalogue items unless explicitly shown as included.
Frequently Asked Questions
Is this standard or oversize?
It is the standard-size piston.
Does it fit M5/M6/M8/M9.8?
No. The previous description was incorrect; this 309-series piston is for the small 2.5/3.5HP two-stroke family.
Are rings included?
Do not assume so. This listing is for the piston; order rings, pin and clips separately unless shown in the product photographs.
How do I choose between standard and oversize?
Measure the cleaned cylinder and follow the service manual's wear and machining limits.
Note: Piston replacement requires precise bore measurement, correct orientation, ring-end-gap checks and professional assembly.
For the products under £150 the shipping is £6.99.
Free delivery for most items over £150.
