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Mercury 390 specs: 390 ci (6.4L) 8-cylinder, 4.05 x 3.784 in (102.9 x 96.1 mm) bore and stroke. Rated 250-266 hp, 1963–1965. Used in the Mercury Marauder.
The Mercury FE (390) is oversquare — the 4.05" bore exceeds the 3.784" stroke by 7.0% — a layout that favors airflow and RPM over leverage at the crank. The 3.784" stroke puts mean piston speed at 4,000 ft/min around 6,350 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 48.8 ci (799 cc).
It is one of 34 engines in the FE family, sitting between the 332 ci and 428 ci members. 5 factory variants share these dimensions, rated from 250 to 266 hp across 1963–1965.
| Displacement | 390 ci / 6.4 L |
|---|---|
| Bore | 4.05" |
| Stroke | 3.784" |
| Cylinders | 8 |
| Configuration | V8 |
| Bore/stroke ratio | 1.07 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 250–266 hp |
| Years | 1963–1965 |
| Bore/stroke character | 1.070 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,784 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 48.8 ci |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1963 | 250 hp | 390 |
| 1964 | 250 hp | 390 |
| 1964 | 266 hp | 390 |
| 1965 | 250 hp | 390 |
| 1965 | 266 hp | 390 |