Morino Associates Inc., a computer systems software company in Vienna, yesterday offered to acquire BGS Systems Inc. of Waltham, Mass., for $27 million.

BGS officials had no comment on the offer, which apparently was unsolicited.

BGS makes, sells and supports software products used to analyze the performance of medium to large IBM computer systems and communications networks.

BGS earned about $63,000 on revenue of $13 million in the fiscal year ended Oct. 31.

"We think the combination of BGS with Morino Associates would strengthen our company, provide value-added benefit to our clients through the integration of our complementary product lines, and would give stockholders of BGS a substantial premium over the recent market price of their common stock," said Mario M. Morino, chairman of Morino Associates.

The offer is worth about $9 a share. BGS stock closed yesterday at $7.75, up $1.25.

Morino said it would finance the takeover through cash reserves and bank credit.

Meanwhile, Morino yesterday reported a 50 percent increase in second-quarter profit, to $3 million (29 cents a share) from $2 million (19 cents) a year ago.

Revenue for the quarter was $12.5 million, compared with $9.3 million for the same quarter last year.

During the first six months of the year, Morino earned $4.6 million (44 cents), up 48 percent from $3.1 million (31 cents) in the first six months of fiscal 1987.

Revenue for the six months rose 35 percent, to $21.8 million from $16.2 million.