whaling ship vs whaler

whaling ship and whaler both are nouns.

Word	Noun	Adjective	Verb	Adverb
whaling ship	Yes	No	No	No
whaler	Yes	No	No	No

As nouns, whaling ship and whaler are synonyms defined as:

whaling ship (noun)	whaler (noun)
a ship engaged in whale fishing	a ship engaged in whale fishing
	a seaman who works on a ship that hunts whales