Reference · Variants

Spitfire Mk.I vs Mk.II — the nine visible differences

WW2 Modeller Hub20255 min read

The Spitfire Mk.II entered service with 19 Squadron in September 1940 — during the Battle of Britain. While externally very similar to the Mk.I, there are nine visible differences that a careful modeller needs to know. Getting them wrong means calling your model something it isn't. Getting them right means building one of the cleanest and most interesting aircraft variants of the entire war.

The key differences

1. Engine — Merlin XII vs Merlin II/III

The Mk.II was powered by the Merlin XII producing 1,175hp against the Mk.I's Merlin II or III at 1,030hp. The external evidence of this is subtle — the Merlin XII used a different supercharger intake profile visible as a slightly different curvature on the lower engine cowling.

2. Exhaust stacks — short ejectors vs early single-point

Early Mk.Is carried single-point exhaust stubs protruding from the cowl. By mid-1940 most Mk.Is had been retrofitted with short ejector stacks. The Mk.II from the outset used the stub ejector type. Most 1:48 kits supply the later ejector pattern which is correct for mid-battle Mk.Is and all Mk.IIs.

3. Carburettor intake

The Mk.II's Merlin XII had a slightly larger carburettor intake under the nose than the Mk.I's Merlin II. This is visible in careful measurement but is difficult to model at 1:48 without dedicated resin.

4. Propeller boss

The Mk.I used a Watts wooden two-blade prop in the earliest examples, quickly replaced by a de Havilland three-blade metal propeller. The Mk.II standardised on the de Havilland constant-speed prop with a slightly different spinner profile than the earliest Mk.I machines. All late-1940 Mk.Is and all Mk.IIs should have the three-blade metal prop.

5. Spinner shape

The Mk.II's de Havilland constant-speed prop had a slightly more prominent spinner than the Mk.I. The difference is subtle but visible in profile shots.

6. Cockpit hood

Some early Mk.IIs began appearing with the revised cockpit hood that had a deeper rearward-sliding section. The Mk.I used the earlier pattern. This is a minor difference that most kits address with optional parts.

7. Armament

Both Mk.I and Mk.II standard armament was eight Browning .303 machine guns. Some Mk.Is were experimentally fitted with two 20mm Hispano cannon replacing the outboard .303s — the 'B wing'. Mk.IIs with this arrangement show visible differences at the outboard gun ports. Standard eight-gun configurations show no visible difference.

8. Oil cooler

The oil cooler under the port wing leading edge was slightly reshaped on the Mk.II. Again, subtle — and most kits supply only one version.

9. Fuselage serial block

The serial number ranges distinguish the marks: Mk.Is ran from K9787 through to approximately X4660 in the BoB period. Mk.IIs began with P7280 onwards. If your decal sheet shows a P7xxx serial, you are modelling a Mk.II and should ensure your kit represents one.

For the modeller

For a BoB battle period build, most Spitfires were Mk.Is. The Mk.II only entered service in September 1940 with 19 Squadron and was not widespread until after the battle closed. If you want to model specifically a Mk.II in the battle, 19 Squadron (QV codes, Duxford) is the correct choice — and the Airfix 1:48 and Arma Hobby 1:72 kits supply markings for this.

For kit recommendations, paint codes and the full squadron reference, see the Spitfire reference page.