DURING THE INITIAL CLIMB AFTER TAKEOFF, THE ENG LOST POWER. SUBSEQUENTLY, THE ACFT COLLIDED WITH TREES AND CRASHED. WATER WAS FOUND IN A FUEL LINE (BTN THE FUEL SELECTOR VLV AND ELECTRIC FUEL PUMP), ELECTRIC BOOST PUMP MANIFOLD, AND CARBURETOR (CARB) INLET STRAINER; HOWEVER, THE FUEL SYSTEM WAS DAMAGED DURING IMPACT AND FIRE SUPPRESSANT CHEMICALS WERE SPRAYED ON THE WRECKAGE. A CHECK OF THE CARB SHOWED THAT IT WAS PROVIDING A LEAN MIXTURE AT LOW POWER SETTINGS AND A RICH MIXTURE AT HI POWER SETTINGS. A TEARDOWN OF THE CARB REVEALED A CRYSTALLINE SUBSTANCE ON THE CARB DIAPHRAGM, AN IMPROPER METERING JET, AND THAT 5 SHIMS WERE INSTALLED IN THE CARB REGULATOR DIAPHRAGM SPRING MECHANISM. THE BENDIX OVERHAUL MANUAL ALLOWED A MAXIMUM OF 2 SHIMS. DURING A POST-ACDNT CHECK, THE ENG OPERATED NORMALLY WITH THE ELECTRIC FUEL PUMP ON, BUT THE ENG STOPPED RUNNING WHEN THE ELECTRIC PUMP WAS TURNED OFF.