The motors were taken from boats floating in the port of Täuffelen on the east side of the lake on either Wednesday night or early Thursday morning, cantonal police said.
Police said they were initially notified of a boat floating in the harbour.
When the boat was brought to the quay a missing motor was noticed.
Further investigation led to the discovery of another 15 motors missing.
The value of the missing motors was estimated by police in the tens of thousands of francs.
Police are looking for people around the marina who may have seen suspicious activity or have other pertinent information.
Anyone with such information is asked to telephone 032 344 51 11.
The theft sparked an angry response from readers of the Bieler Tagblatt, the Biel newspaper.
One reader complained that with its now open borders Switzerland has become “a Europe-wide self service store”.
Overly tolerant policies from Swiss politicians just invite thefts and break-ins, the reader commented.