cruiser vs powerboat

cruiser and powerboat both are nouns.

Word	Noun	Adjective	Verb	Adverb
cruiser	Yes	No	No	No
powerboat	Yes	No	No	No

As nouns, powerboat is a hypernym of cruiser; that is, powerboat is a word with a broader meaning than cruiser:

cruiser: a large motorboat that has a cabin and plumbing and other conveniences necessary for living on board
powerboat: a boat propelled by an internal-combustion engine

Other hypernyms of cruiser include motorboat.

cruiser (noun)	powerboat (noun)
a large fast warship; smaller than a battleship and larger than a destroyer	a boat propelled by an internal-combustion engine
a large motorboat that has a cabin and plumbing and other conveniences necessary for living on board
a car in which policemen cruise the streets; equipped with radiotelephonic communications to headquarters