A tanker carrying 375,000 gallons of fuel oil ran aground today in the Delaware River but was refloated a few hours later without any apparent leaks, authorities said. The Norwegian tanker Manhattan Princess, operated by Ahlers Shipping of Belgium, grounded on a muddy bottom on the New Jersey side of the river at 12:45 a.m. today, said Coast Guard Lt. Pete Hoffman. Coast Guard Lt. Pete Hoffman said two tugboats pulling on the tanker got it off the bottom with little trouble after high tide arrived about 9:15 a.m. Investigators found no leakage or ship damage, he said. The ship, drawing 37 feet of water, was en route to the Hess terminal in Pennsauken, N.J., when it wandered out of the 40-foot deep channel. An investigator went along with the tanker to look into the cause of the grounding, Hoffman said. The ease of refloating the tanker was an indication that the tanker wasn't very hard aground on the soft, muddy bottom, Hoffman said, and it also suggested that there wouldn't be any damage to the hull.