Designation No.5a
Bore 2 1/4 inch
Stroke 2 inch
Configuration Vertical single cylinder
Height 15 inches
Extra equipment Drain cocks
Feed pump
Displacement lubricator
Reversing gear
Taps required 2, 4 BA
1/4 x 32 tpi
1/4, 3/8, 1/2, 5/8 x 26 tpi
Notes Large engine suitable for driving dynamos, pumps and often seen in small full-size boats as part of a marine plant. Stuart claimed 5/8 bhp at 1000 rpm on 60 psi pressure. A special large-size displacement lubricator was available for this engine.

The example below is fitted with a mechanical cylinder lubricator.