Spit Mk1 Boost?

[Crumpp]

without damage to the engine.

That is an entry in a Squadron logbook. The man who wrote that is not a technical expert in engines. He is an operator not an engineer.

The engineers clearly disagree with this operator in the instruction under entry number 11 for AP 1590B/J.2-W Merlin II and III Use of +12lbs Boost Pressure - Alterations and Precautions.

Paragraph 11 clearly states:

The use, in an emergency, of this high boost pressure is a definite overload condition on the engine....