On May 27, 1993, about 1320 central daylight time, a Piper PA-23-160 airplane, N3333P, operated by Crystal Shamrock, Inc., sustained substantial damage when it collided with trees approximately four miles north of Ely, Minnesota. The commercial pilot and the sole passenger aboard were seriously injured. The flight departed Hallock, Minnesota about 1100, with an intended destination of Cook County Airport, Grand Marias, Minnesota. Instrument meteorological conditions prevailed for 14 CFR Part 91 flight, and an instrument flight plan was filed. The pilot reported a relatively slow loss of power from the left engine while in cruise at 7,000' MSL. He said the power loss developed over several seconds. The pilot wrote in his report to the NTSB that he feathered the left engine and made a diversion to Ely, Minnesota. He was unable to maintain altitude, and complained of excessive drag from an unknown source on the airplane. He wrote that it became apparent that the airplane would not reach Ely due to his inability to maintain altitude, and he elected to make a forced landing into the tree tops. During the flight, the pilot said the main landing gear kept creeping down and he had to keep "snugging" it up by putting the gear handle in the up position. Once the left engine ceased to run, he said he used the emergency hydraulic hand pump to accomplish the same task. According to the pilot's written statement, he was aware of the sagging gear problem prior to the flight, and that it was necessary for him to bring the gear up every 3 to 5 minutes. He said that the main landing gear system apparently had a slow leak, and it was scheduled for repair soon. He also wrote: "In retrospect, I believe this seemingly minor problem may have been of critical significance in causing this accident. I think given a few more seconds of time, I may have been able to recognize this as the source of drag and eliminate it and avoid the crash-landing." The airplane's left engine was examined in the field by an FAA inspector. His report (appended) notes that all of the left engine spark plugs were very blackened, and that the fuel sample taken between the fuel pump and carburetor was dirty and watery.