Mercury 171ci specs: 3.661 x 2.70 in (93 x 68.6 mm) bore and stroke, shared by all 2 versions. Displacement, compression and factory ratings, plus rod ratio.
| Displacement | 171 ci |
|---|---|
| Cylinders | 6 |
| Bore | 3.661" |
| Stroke | 2.700" |
| Compression | 8.7:1 |
| Years | 1976–1979 |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| Cologne 2.8 | 171 ci | 3.661" × 2.7" | — | — |
| Mercury 171ci (1979) | 171 ci | 3.661" × 2.7" | 8.7:1 | — |
All are oversquare — bore larger than stroke, which favours revs over low-end torque.
Each engine page carries rod ratio, mean piston speed, bore/stroke character and cylinder head specs where published, and links into the calculators with its dimensions already filled in.