The term motorsailer often used as a criticism for poorly designed sailboats. A good motorsailer is specifically designed as such, and has many advantages over the average sailboat..
This is what Bill Kimley from Seahorse
Marine describes them.
"So what's different about a motorsailer? The motorsailer is a vessel that sort of sails without a motor pretty well, but not real close to the wind, and can motor along without sails OK, but may be a little stiff. A stiff
hull is shaped to resist rolling. It carries sail well but it likes to float with its beam
water line parallel to the water surface. A lumpy sea presents many inclined water surfaces and a stiff
hull will snap around trying to parallel each one as it passes.
The
designer of a motorsailer has to make the decision to exclude good upwind performance. Accepting that compromise allows a lot of neat things to happen, lighter weight, shallower
draft, 5 feet is the max for most
canal systems, and a more yacht
trawler like hull shape with its large accommodations, especially in the aft
cabin. But the neatest thing of all is the way the large motor and large sailing rig of a true motorsailer, designed with a nice slippery hull,
work in harmony, the motor taking over in the lulls and the rig taking over in the puffs, to provide a surprisingly fast,
fuel efficient and comfortable
passage."