Mayor Marion Barry yesterday proposed a salary increase of 5 percent and a 2 percent bonus for District government workers not covered by collective-bargaining agreements. The wage increase proposal provides for $2,500 raises for his administration's top managers.

Barry's proposal would give the pay increase, effective Oct. 1, and the one-time-only bonus to 8,771 city government employes. The other three-fourths of the city work force is covered by collective-bargaining agreements, Barry said.

The pay raise and bonus would cost the government $10.2 million, the mayor said. There are no funds currently earmarked in the budget for the coming fiscal year to pay for the package, but Barry said the city will be able to meet the cost.

The wage increase would raise the cap of $50,112 on D.C. government salaries other than the mayor's to $52,618. That would mean a $2,500 raise for city department heads, who currently make the top allowable salary. Barry said that was necessary "to enable the District to attract and retain quality personnel."

In a letter to City Council Chairman Arrington Dixon asking the council to approve the measure, Barry wrote that the pay increase would keep salaries of District government workers in line with those of suburban jurisdictions.

He noted that President Reagan has proposed a 4.8 percent increase for federal workers for the fiscal year beginning Oct. 1. Many District workers were angered last year when Barry proposed a 5 percent increase, while federal workers received 9.1 percent.

Barry said he rejected the idea of giving larger increases to employes at the bottom of the city salary scale and smaller increases to more highly paid workers. He said that would lessen incentive to advance to higher salary grades.

Barry's proposed budget for the coming fiscal year contains no money for pay increases. But he said he is banking on a stronger-than-expected revenue flow, about $9 million projected from the planned sale of surplus government property and "greatly improved" relations with the congressional committees that hold the city's purse strings to provide the money for the increase.

Barry, who is expected to seek reelection, said in a prepared announcement of the proposal that holding the pay package to 5 percent plus a bonus would allow him to keep his pledge of no new or increased taxes for 1982.

The 5 percent increase would go into effect Oct. 1, under Barry's plan. Employes would receive the 2 percent bonus in December. Only full-time workers would be eligible for the bonus, though some part-time employes could qualify for a partial bonus payment.