Prince George's County high school coaches with nine or more years experience in major sports will receive stipend increases of more than 61 percent over the next three years, according to a new three-year contract agreed to by county teachers union representatives last week.

Coaches in other sports will receive increases of 33 percent or more, according to the agreement.

Presently, Prince George's County varsity football coaches make $1,298, less than half than their counterparts in Montgomery County. Prince George's assistant coaches make 70 percent of the head coach's stipend, while Montgomery assistants earn more than $2,200.

Next year, under the new pay formula, all Prince George's coaches will receive a 10 percent increase in their stipends.

In the ensuing two school years, the amount of an individual coach's increase will be determined by experience. Coaches with five years experience or less will receive another 10 percent increase in 1987-88, but those with greater experience will get a 20 percent hike in their stipends. The two-tiered formula adds a third class of coaches in 1988-89, those with 11 or more years coaching experience. Those senior coaches would receive another 20 percent raise, while the other two classes would receive lesser increases.

Initial stipends would be determined by the time commitment level required by each sport. Again, Prince George's 13 interscholastic sports were divided into three categories. Level 1 sports, which could pay senior coaches $2,090 by 1988-89, include football, girls and boys basketball, baseball, wrestling, softball and outdoor track. Level 2, which could pay up to $1,515 within three years, includes boys soccer, indoor track and girls volleyball. Level 3, which still will pay less than $1,000 even to coaches with 11 or more years experience at the end of this new contract, includes tennis, golf, cross country and swimming.

Prince George's County does not fund varsity teams in girls soccer, coed volleyball and lacrosse.

Parkdale's spring sports teams still must play their home games on the road this season, but soon that will not always mean at their opponents' home fields. Beginning in May, Parkdale home baseball and softball games will be played at the Lanham Boys Club or Walkers Mill Park in District Heights . . . The third annual Crown Maryland High School all-star baseball game has been set for June 14 at Memorial Stadium. Organized by Arundel Coach Bernie Walter, 30 graduating seniors from the throughout the state will be selected by a panel of coaches by June 1.

Sherwood wrestling Coach John Ellinger has quit to devote more time to his job as soccer coach at the University of Maryland-Baltimore County . . . Queen Anne's Leslie Oliveri and Dawn Gould teamed for a 17-1 no-hitter against Field last Wednesday.