On July 15, 2006, about 1810 coordinated universal time, a pilot ditched a Cessna R172K II, N1209V, near Hagatna, Guam. Micronesia Aviation Systems, Inc., was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The certificated commercial pilot and two passengers sustained minor injuries; the airplane sustained substantial damage to the firewall. The local sight seeing flight departed Guam International Airport in Hagatna about 1805. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot reported to the Federal Aviation Administration that the airplane was climbing through 1,500 feet. The engine began to run rough, and he tried to smooth it out using the mixture. It began sputtering as he tried to return to the airport for a landing on runway 06L. However, it's condition worsened, and then the engine quit producing power. He ditched in a nearby bay. A Federal Aviation Inspector supervised examination of the airframe and engine. The airplane sustained damage to the firewall where the engine cradle attaches to the airframe. The cradle tweaked to the right, wrinkling the airframe just a little aft of the firewall. He observed a hole in the top of the case at the number four cylinder. He noted that the number four connecting rod fractured and separated. After being in the salt water, he reported that the engine had corroded and could not be further disassembled. The engine had been flown 1,500 hours past the manufacturer's recommended time between overhaul.