what is difference between boatload and carload
From boat + load. Notionally, because the commodity in question might have constituted the entire load of a cargo ship or boat.
- (Received Pronunciation) IPA(key): /ˈbəʊtˌləʊd/
- (General American) IPA(key): /ˈboʊtˌloʊd/
boatload (plural boatloads)
- Cargo or passengers that fill a boat.
- (slang) A large quantity.
- Synonyms: see Thesaurus:lot
- He showed up an hour later with a whole boatload of hamburgers, chips, cookies, and assorted other munchies, not to mention sodas and beer, and we all fell in and stuffed ourselves silly.
- 2006, Rob Pegoraro, “Waiting for the Winner of a High-Definition High Noon”, The Washington Post, December 10 
- What’s a fair price to pay for video perfection, or even something that looks a lot like it? In the case of high-definition movie discs, the answer may not just be “a boatload of money,” but having to keep two incompatible players under the TV set.
- “boatload”, in Lexico, Dictionary.com; Oxford University Press, 2019–present.
From car + load
- (UK) IPA(key): /ˈkɑːləʊd/, [ˈkʰɑːləʊd]
- (US) IPA(key): /ˈkɑɹloʊd/, [ˈkʰɑɹloʊd]
carload (plural carloads)
- The contents of an automobile (passengers, supplies, etc.) for one trip.
- (rail transport, US, Canada) The quantity of goods that can be carried in a freight car.
- “carload”, in Lexico, Dictionary.com; Oxford University Press, 2019–present.
- “less-than-carload”, in Merriam–Webster Online Dictionary.