Defense contractor General Dynamics Corp reported a better-than-expected quarterly profit on Wednesday and boosted its full-year forecast as revenues improved in all its business segments.

The maker of tanks, ships and submarines said net earnings came to $618 million, or $1.60 a share, for the second quarter, compared with $641 million, or $1.60 a share, a year earlier.

Excluding discontinued operations, profit was $1.61 a share, topping analysts' average forecast of $1.57, according to Reuters Estimates.

Revenue rose 11 percent to $8.1 billion.

In early notes, analysts cited better-than-expected margin performance, particularly in the aerospace division, which has been hurt by a slump in the business jet business.

Aerospace operating margins came to 15.2 percent in the second quarter, down from 18.1 percent a year earlier but up from 13.7 percent in the first quarter.

Sanford Bernstein analyst Douglas Harned said Gulfstream, the company's business jet unit, booked positive net order flow in the second period after reporting net cancellations in the first quarter.

Revenue in aerospace rose 6.5 percent, helped by the acquisition of Jet Aviation in 2008, but operating profit fell 10.4 percent. Combat systems, which supplies tanks and machine guns, had a revenue increase of 19 percent, while operating profit rose 6 percent.

The marine systems and information systems divisions posted revenue increases of 17 percent and 4 percent, respectively.

General Dynamics said it now expects full-year profit from continuing operations of $6.05 to $6.15 a share, compared with its April forecast of $6.00 to $6.10 a share.

General Dynamics shares were at $52.77 in premarket trade, down from a Tuesday close at $53.74 on the New York Stock Exchange.

(Reporting by Karen Jacobs; editing by John Wallace)