the hazards of the gasoline-engines on board of s-boats was proven again when a s-boat burned out in the harbour of priwall at travemünde; also at sea this experience was confirmed and some crews had to leave their boats until the burning boats could be extinguished by cutting of the oxygen-supply or by blowing in tetrachlorine.

How would the previous sentence be correctly capitalized?
The hazards of the gasoline-engines on board of S-Boats was proven again when a S-Boat burned out in the harbour of Priwall at Travemünde; also at sea this experience was confirmed and some crews had to leave their boats until the burning boats could be extinguished by cutting of the oxygen-supply or by blowing in tetrachlorine.