Genuine Tohatsu Crankshaft A 309-00031-0 M2.5A2 M3.5A2/B2
309-00031-0
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Tohatsu Crankshaft A
Genuine 309-00031-0 | 2.5/3.5HP two-stroke
Genuine Tohatsu Crankshaft A for legacy 2.5HP and 3.5HP two-stroke powerheads that specify 309-00031-0. Correct crankshaft selection is controlled by the exact model, production serial and suffix shown in the OEM piston/crankshaft diagram.
Key Features
- ✔ Genuine Tohatsu OEM internal-engine component
- ✔ Crankshaft A specification
- ✔ Factory part number 309-00031-0
- ✔ For selected 2.5/3.5HP two-stroke powerheads
- ✔ Supplied as one crankshaft component
Technical Specs
| Part type | Crankshaft A |
| Engine cycle | 2-stroke |
| Power family | 2.5HP / 3.5HP |
| Manufacturer number | 309-00031-0 |
| Supply | 1 genuine Tohatsu crankshaft |
| 4Boats SKU | 309-00031-0 |
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.
Serial note: M2.5A2 applications must be checked against the 90713-up catalogue breakpoint. For M3.5A2/B2, confirm that the diagram specifically calls for Crankshaft A 309-00031-0 rather than another suffix.
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 MFS four-strokes; not for M5, M6, M8, M9.8, M15, M20 or M25; and not a substitute for 309-00034-0 or 3F0-series crankshafts.
Part Number Cross Reference
| Tohatsu | 309-00031-0 |
| Dealer format | 309000310 / 309000310M |
| Nissan Marine | Use exact 309-00031-0 diagram reference |
| 4Boats SKU | 309-00031-0 |
Do not combine this A-variant listing with crankshaft D or complete crankshaft-assembly numbers without catalog confirmation.
Frequently Asked Questions
Is this genuine Tohatsu?
Yes. The listing identifies a genuine Tohatsu crankshaft.
Does it fit MFS15D, MFS20D or MFS25D?
No. The 309-00031-0 catalogue family is for legacy 2.5/3.5HP two-strokes, not those four-stroke engines.
Why must the serial number be checked?
Tohatsu used different crankshaft variants and production breakpoints within similar model names.
Are bearings, seals or connecting-rod parts included?
Only the crankshaft component shown is included unless the product photographs explicitly show additional parts.
Note: Crankshaft replacement requires full powerhead inspection, measurement and professional assembly to the Tohatsu service limits and torque specifications.
For the products under £150 the shipping is £6.99.
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