Prince William County Executive Robert S. Noe Jr. proposed yesterday a $135.7 million budget for fiscal 1986 that calls for a 17.1 percent increase in county spending and would boost the typical homeowner's real estate taxes by $80 a year.

The budget, which must be approved by the county Board of Supervisors, would require a 4-cent increase in the county's real estate tax, to $1.46 per $100 of assessed value, and the imposition of a business, professional and occupational license tax, designed to raise $1.9 million a year.

Noe said that the increase would help pay for the facilities and services voters in the fast-growing county are demanding, but his proposal for the business tax immediately came under fire from a business group that called it burdensome.

"A lot of our members are ma and pa businesses, or professionals, who have never been hit by such a tax before," said Prince William County Chamber of Commerce President Nicholas Carosi. "They worry that it's going to hurt their competitive edge in the metro area."

Schools account for 51.4 percent of Noe's overall budget and would get a 12.5 percent increase in funds, growing from $62 million this year to $69.8 million.

Real estate taxes for the owner of the average home in Prince William, now assessed at $78,600, would increase $80, because of the higher tax rate and the impact of an average 4.5 percent increase in assessments. The average homeowners' real estate taxes would rise from $1,068 to $1,148, county officials said.

Noe warned that the coming fiscal year is a "pivotal time" for the county, which is the second largest jurisdiction in Northern Virginia and the only one without a business license tax. The county is in transition from a predominately rural and suburban bedroom community to a more economically diverse area, he said.

"Our citizens know about services provided to the north of us and expect similar services. They see that our real estate tax is essentially the same as Fairfax, and higher than Arlington, and expect a favorable comparison in services. Many fail to realize the much larger economic base generating more tax dollars per penny in those jurisdictions," he said.

Noe's budget also calls for a 4 percent cost-of-living increase for county employes, the same as proposed for county workers in neighboring Fairfax County; the equivalent of 79 new full-time jobs, and the elimination of a salary cap for certain positions.

Additionally, Noe recommended a pay plan that would adjust some salaries to maintain Prince William's fourth-place ranking in the Northern Virginia market, behind Fairfax, Arlington and Alexandria.

Supervisors are scheduled to vote on the budget April 23.

Noe urged the county to continue to diversify its tax base and look for new taxes, including a $25 fee for amusement-ride inspections, $5 to $15 for various occupancy permits, and the business license tax.

He recommended that the board ask vote to approve a $12.8 million bond referendum in 1986 to pay for the new administration building renovations and other items; a $24.2 million bond in 1987 for a high school and school improvements, and a $18.2 million bond in 1989 to pay for, among other things, public works improvements.

Despite what county officials consider great demand for new facilities, Prince William voters have defeated nine of 11 bond proposals in the past decade. As a result, the Board of Supervisors has used regular budget funds to pay for facilities, such as a new jail and expanded library services.