[Juha]

Hello
I interpred Laurent's message that the boats and flame-throwers were damaged and destroyed in Dunkerque. Easiest way to explain the flame-throwers is that they were destroyed when a magazine where they were stored was hit.
I know nothing on Stormboats but Sturmboot is a small boat most suitable to river crossing, powered by an outboard engine, carrying c. a rifle squad or 10 men, driven by a pioneere. Maybe the best way to translate its name is an assault boat.

HTH but maybe only a wrong track
Juha