By late morning, shares had added 13.2% to $56.45. Trading volume of 2.3 million was more than double its three-month average daily volume of 1 million.
The company, which manufactures portable and industrial generators, posted fourth-quarter net income of $1.11 a share. Analysts surveyed by Thomson Reuters had expected per-share earnings of 90 cents.
Revenue of $376.2 million increased 10% on the year-ago quarter and beat expectations by $13 million. Sales growth was driven by an increase in shipments of home standby generators and commercial and industrial products, as well as increased revenue from recently-closed acquisitions.
In November, the company completed its acquisition of Baldor Electric's generator division Baldor Generators. Ottomotores, a leading manufacturer in Mexico, was acquired in December 2012 and Europe-facing Tower Light was purchased in August, both of which have contributed to overall sales growth over fiscal 2013.
"In addition to our organic growth, we executed on three important acquisitions that provide additional product breadth and global scale to our C&I business and improved balance to the overall company," said CEO Aaron Jagdfeld in a statement.
In fiscal 2014, management expects net sales growth in the mid-single digit range.
"Heading into 2014, our team remains focused on the substantial penetration opportunity that exists for residential and light commercial standby generators, as well as increasing our share of the C&I market through our recently expanded product offering and our continued focus on natural gas generators," added Jagdfeld.