Thieves made off with engines from three boats moored at Belle Isle Marina in Dogdyke.
Items taken include a 15HP Mariner outboard engine which is black and red in colour, as well as a 15HP Yamaha outboard engine. A remote control for an engine was also stolen and locks damaged.
Police have now decided to issue an appeal to catch the people behind the incidents, which took place between 8.30pm on Wednesday, May 28, and 8am the following morning.
PC Dave Eldridge, of Horncastle Police Station, wants anyone with information about the thefts to call him on 101, quoting incident number 72 of May 29.
You can also report crimes anonymously by contacting Crimestoppers on 0800 555 111.