- Jun 3, 2012
Tale of woe here. My Yanmar engine manual states that the idle speed should be 800 and to rev engine up just before shutting down to clear carbon out of the head. Never had a carbon problem and observed that my idle has always been 1000. Changed two things to bring on near disaster. First I adjusted my idle down to the recommended 800. Second I stopped revving the engine before shutting down. The other day when I tried to start the engine up all I got was a thunk. Checked voltage on start battery which was ok and tried again. Blew a 250A fuse on the start battery circuit. Good thing, that. Investigation found that the exhaust elbow and hose was full to the top with water. The engine was hydrolocked. Repairs consisted of removing elbow (in fine shape) and draining exhaust hose. Removed injectors, tied off decompression lever to hold valves open. Rotated engine by hand while blowing out water through injector ports with my portable nail gun air compressor. I had a dummy injector for compression testing that came in handy. After reassembly, all is well and no damage. The moral here is beware of slow idle that may not completely expel water in the exhaust system and be sure to rev up when shutting down to blow all remaining water out.