"Hurl" can mean various things and yes if we go for a "hurl" in the car then we are just going for a ride or drive in the car. But it also means doing something fast or forceful. If you hurl a stone then you know it is being thrown with force; if the rain is hurling down then you know it is very heavy rain not just a wee shower; and if a car is hurling down the hill then you know it is going very fast, possibly too fast. So for me the use of 'hurl' in the context here means more than simply carry. Closer alternative words for 'hurl them on" would possibly be to 'speed them on" so I think Reiver 2 already had that meaning.