Every small boat that I know of can use or uses an inverter to convert DC mains to 115V 50 of 60 HZ, so commercial equipment
can be run on board.
The efficiency of a larger inverter is about the same as the smaller ones and you get the benefit of a permanent mount, so space is about the only reason of going with a lower power inverter.
Those home type sewing machines ran off a series AC motor and is normally not sensitive to input waveshape so sine wave inverter is not required.
I use a Wagen 3KW modified square wave inverter off the house bank supply for most AC @ line voltage. .
I run a SINGER 401A for sewing, it is all gear
driven with no belts or cheap
. Chassis is cast aluminum
. Well supported currently on ebay.
It uses cams to provide programming of stitches.
I have found some issues: The bobbin is small and will not supply much #70 thread, the largest needle is a #18.
Thread tensioning is basically an art on the heavy thread on heavy cavass but, the sail cloth and marine
fabrics are not as thick as canvas
and sew nicely. Got 6 yards of sunbrella from sailrite the other day for next project
Since all the drive parts
are machined steel
or bronze it needs much attention when stored on a boat or it will rust, probably true for the sailrite machines too because they are mostly cast iron and steel
Sailboat with no sewing machine, such a world.