Assuming you want a
boat sewing machine, and a walking foot isn't a must-have (your singer doesn't have one), you should also consider other older all metal mechanism machines with zigzag. The Pfaff 130 is bulletproof (the 230, 260, 360 etc. also good) and well known among sailors.
ebay Aus has one for $30 right now if you can negotiate the
delivery -
PAF 130 Sewing Machine | eBay
and another:
* PFAFF 360 AUTOMATIC SEWING MACHINE, CRAFTS, SEWING, COLLECTABLE | eBay