I'm confused as to why it wouldn't be considered parking. The boat/trailer/truck are parked on the side of the road. What else is there to the definition of a parked vehicle or trailer?
Either way, it sounds like you need to consult your local ordinances.
Specifically §108-3:
No person shall park on any public roadway or dedicated private roadway in a residential district any recreational vehicle whose length is greater than 240 inches, or whose width is over 84 inches, or whose height is over 84 inches, or whose weight exceeds 5,000 pounds. The parking of boats or trailers on public roadways in residential districts is prohibited.
It's also worth noting that there is a maximum length of vehicle that can be parked in residential areas in §108-2 A:
No person shall park in any residential district any tractor, trailer, tractor and trailer, or any combination thereof, bus, dump truck, oil truck or any other vehicle whose length is greater than 240 inches, or whose width is over 84 inches, or whose height is over 84 inches, or whose weight exceeds 5,000 pounds, except when serving a permitted use.