The commander of a Coast Guard training ship who admitted turning his vessel into the path of an oncoming freighter, causing a collision that killed 11 crewmen, was convicted yesterday on a minor offense carrying a maximum sentence of three month's in prison.

A military court sitting in Yorktown, Va., found Chief Warrant Officer Donald K. Robinson, 48, guilty of neglect, a lesser offense than prosecutors had sought for his role in the Oct. 20, 1978, collision. The jury of seven commissioned officiers will return Monday to fix Robinson's punishment.

Robinson, who worked his way up from the enlisted ranks to command the service's 51-year-old cutter Cuyahoga, had been blamed by two investigative panels for turning his ship into the path of a large Argentine freighter in Chesapeake Bay at the mouth of the Potomac River. The Cuyahoga sank moments later in what was considered the worst accident in Coast Guard history.

Robinson's lawyers conceded during his five-day trial in the Cuyahoga's home port that he had acted improperly. The jury apparently accepted the defense argument that a respiratory illness and lack of sleep caused Robinson to believe that the vessel he saw that clear night was a fishing boat, not a 500-foot freighter.

After 12 hours of deliberation, the jury rejected the charge against Robinson of negligently hazarding his vessel, which could have carried a maximum penalty of two years at hard labor and dismissal from the service.

Robinson, a 27-year veteran of the Coast Guard, was orginally charged last April with involuntary manslaughther and destruction of government property in addition to negligence. The first two charges were dropped in June when a military judge ordered that the Coast Guard would have to conduct another investigation of the accident if it wished to try Robinson for the more serious offenses.

The prosecution argued that Robinson's decision to turn the Cuyahoga had been criminally negligent.

Trial testimony indicated, however, that Robinson had been weary from sleepiness due to a pulmonary disorder that had gone undiagnosed by military doctors from March 1978 until December 1978, two months after the accident.

The defense argued that Robinson had done everything required by regulations when he took visual bearings on the courses of the two ships. If the captain's judgment was bad, the defense argued, it was because of exhaustion, not negligence.

Prosecutors questioned the seriousness of Robinson's illness and claimed that he should have determined the exact course and speed of the approaching freighter, Santa Cruz II.

Military Judge R. A. Appelbaum, a Coast Guard commander, told the jury Friday that it had to determine whether Robinson's actions were reasonable and prudent and whether he was healthy enough to know what he was doing.

Robinson's attorney, Jerome Flanagan, said yesterday that "we are quite happy with the rejection of the negligence charge. [the jury] was apparently convinced that he did have a serious illness."

Flanagan said that Robinson, the first Coast Guard captain to face a court-martial since 1966, would not comment on the case until after his sentencing.

Robinson, who has been in charge of security at the Yorktown training base since the accident, said in June that the tragedy "is not just something you shrug off." He added that he hoped he would not have to leave the Coast Guard because of the tragedy and said he would like to command another ship.

Salvage crews managed to raise his last ship, the Cuyahoga, from the floor of the bay, but surveyors found it too badly damaged to be repaired. It was the only ship of its class in the Coast Guard and was the oldest cutter in service when it sank.

Robinson, who was won four good conduct medals during his career, had taken command of the Cuyahoga in June 1977, supervising its use as a training vessel.

On the night of Oct. 20, 1978, Robinson was on the bridge as it headed from Yorktown into the Potomac River shortly after 9 p.m. with a crew of 29.

Believing that he was overtaking a small fishing boat, Robinson ordered a left turn that put him in the path of the Santa Crutz II. The freighter rammed into the side of the Cuyahoga, causing it to sink within minutes. Most of the 11 crew members who died were officer trainees.