Munster Lass first appeared in online volumes of Lloyd's Register (LR) in 1768.

[4] On 28 May near St Lucia Shelanagig encountered the French fleet under Comte de Grasse, which captured her.

Munster Lass had put Lieutenant Johnston of the Royal Marines on shore at Tyrrel's Bay (11°17′53″N 60°32′02″W / 11.298°N 60.534°W / 11.298; -60.534) in Tobago and it was he that reported back to Rodney on 4 June that the French had captured Tobago.

The Royal Navy's West India squadron recaptured Schelanagig in 1782, but there is no report of her subsequent disposition.

When he finally spotted de Grasse's fleet, the latter was sailing for Grenada with 24 ships of the line to Rodney's 20.