A man accused of unleashing a string of curse words after he tumbled out of his canoe last summer was convicted today of violating an 1897 ban on swearing in front of children.

Jurors in rural Arenac County, 130 miles north of Detroit, deliberated less than an hour before convicting Timothy Joseph Boomer, 25. The factory worker from the Detroit suburbs could be jailed for 90 days.

He did not deny letting off steam after his canoe hit a rock on the Rifle River last summer, but he said he did not see any children and that his shouts were in jest.

"Timothy Boomer at worst said an 'f-word' or two when he fell into the Rifle River," defense attorney William L. Street told the jury in his closing statement. "It was not the sort of event that has now been exaggerated and blown all out of proportion."

But Richard E. Vollbach Jr., the prosecutor, said witnesses testified that Boomer "used the 'f-word' at least a few dozen times with children present . . . anywhere between 25 and, I believe, 70 times."

Police began patrolling the river last summer after representatives of campgrounds and property owners complained that drunken, rowdy boaters were getting out of hand.