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Mercury 2300 HSO OHV specs: 140 ci (2.3L) 4-cylinder, 3.78 x 3.126 in (96 x 79.4 mm) bore and stroke, 9:1 compression. Rated 100 hp, 1988.
The Mercury 2300 HSO OHV is oversquare — the 3.7795" bore exceeds the 3.126" stroke by 20.9% — a layout that favors airflow and RPM over leverage at the crank. The 3.126" stroke does not reach 4,000 ft/min of mean piston speed until about 7,700 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 35.0 ci (574 cc).
9:1 on iron heads is low by modern standards and generally happy on regular pump fuel.
It is one of 6 engines in the Lima family, all of them 140 ci — the differences between them are in compression, heads and rating, not displacement.
| Displacement | 140 ci / 2.3 L |
|---|---|
| Bore | 3.7795" |
| Stroke | 3.126" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 9:1 |
| Bore/stroke ratio | 1.209 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | SOHC |
| Fuel type | gas |
| Advertised HP | 100 hp |
| Years | 1988 |
| Bore/stroke character | 1.209 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,126 ft/min — conservative for a street engine |
| Displacement per cylinder | 35.0 ci |
| Static compression | 9:1 — low by modern standards, generally happy on regular pump fuel |
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2 factory vehicles, 1985–1991. Each year opens that model's engine table.