Would a 150kg (boat and engine) set up on a launching trolley be too heavy for one person to launch and recover from a shallow slipway? The distance from the secure storage area available to the water would be about 20 metres.
The thought of being able to leave the boat set up near the water, under a cover, and launch it without a car is quite appealing.
Should be ok if the trolley is a goodun. Pneumatic tyres would prob be best, rather than solid plastic/nylon. Less rolling resistance when well inflated.
Much of it is about the balance point of the trolley and how much weight you are lifting on the handle. Assuming balanced OK so the lift is OK you could trundle that weight for hundreds of meters on hard surfaces.
My SIB setup with boat/motor/fuel/kit would be 140-150kg and we trundle that on its transom wheels for 300m at our most frequent launch site.
