keelboat vs river boat

keelboat and river boat both are nouns.

Word	Noun	Adjective	Verb	Adverb
keelboat	Yes	No	No	No
river boat	Yes	No	No	No

As nouns, river boat is a hypernym of keelboat; that is, river boat is a word with a broader meaning than keelboat:

keelboat: river boat with a shallow draught and a keel but no sails; used to carry freight; moved by rowing or punting or towing
river boat: a boat used on rivers or to ply a river

keelboat (noun)	river boat (noun)
river boat with a shallow draught and a keel but no sails; used to carry freight; moved by rowing or punting or towing	a boat used on rivers or to ply a river