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Mercury 4.0 SOHC specs: 245 ci (4.0L) 6-cylinder, 3.953 x 3.323 in (100.4 x 84.4 mm) bore and stroke. Rated 205-210 hp, 1997–2010. Used in the Ford Explorer.
The Mercury 4.0 SOHC is oversquare — the 3.9528" bore exceeds the 3.3228" stroke by 19.0% — a layout that favors airflow and RPM over leverage at the crank. The 3.3228" stroke does not reach 4,000 ft/min of mean piston speed until about 7,200 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 40.8 ci (669 cc).
It is one of 10 engines in the Cologne family, sitting between the 170 ci and 256 ci members. 17 factory variants share these dimensions, rated from 205 to 210 hp across 1997–2010.
| Displacement | 245 ci / 4 L |
|---|---|
| Bore | 3.9528" |
| Stroke | 3.3228" |
| Cylinders | 6 |
| Configuration | V6 |
| Bore/stroke ratio | 1.19 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | SOHC |
| Fuel type | gas |
| Advertised HP | 205–210 hp |
| Years | 1997–2010 |
| Bore/stroke character | 1.190 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,323 ft/min — conservative for a street engine |
| Displacement per cylinder | 40.8 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 |
|---|---|---|
| 1997 | 205 hp | 4.0 SOHC |
| 1998 | 205 hp | 4.0 SOHC |
| 1999 | 205 hp | 4.0 SOHC |
| 2000 | 205 hp | 4.0 SOHC |
| 2001 | — | 4.0 SOHC |
| 2002 | — | 4.0 SOHC |
| 2002 | 210 hp | 4.0 SOHC |
| 2003 | — | 4.0 SOHC |
| 2003 | 210 hp | 4.0 SOHC |
| 2004 | 210 hp | 4.0 SOHC |
| 2005 | — | 4.0 SOHC |
| 2005 | 210 hp | 4.0 SOHC |
| 2006 | 210 hp | 4.0 SOHC |
| 2007 | 210 hp | 4.0 SOHC |
| 2008 | 210 hp | 4.0 SOHC |
| 2009 | 210 hp | 4.0 SOHC |
| 2010 | 210 hp | 4.0 SOHC |