Mercury 351W Specs

Mercury 351W engine specs: 351 ci (5.8L), 8-cylinder, 4" bore x 3.5" stroke, 9.5:1 compression.

Dimensions

Displacement351 ci / 5.8 L
Bore4"
Stroke3.5"
Cylinders8
Compression ratio9.5:1
Bore/stroke ratio1.143

Construction

Block materialcast iron
Head materialcast iron
ValvetrainOHV
Fuel typegas
Advertised HP250 hp

What these numbers mean

Bore/stroke character1.143 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves
Mean piston speed at 6,000 RPM3,500 ft/min — conservative for a street engine
Displacement per cylinder43.9 ci
Static compression9.5:1 — in the range that usually runs on pump premium

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Variants sharing these dimensions (2)

These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.

YearAdvertised HPCode
250 hp351W
250 hp351W, 351C

Vehicles (7)

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