From: Bob Smith, bobsmithadc@juno.com Dear Randy: Having built the engine in your boat and supplying same to the builder I have heard the problem before. Unfortunately, there are many variables all of which add up to your jittery jaw. Understanding what you have and then studying the problem must first be done. The solution is likely to be a multi-facetted program. We supplied three different types of mounts to the yards building the DeFever Boats in 1978. A brief description of the mounts construction and base foot print will identify for me. There was one particular mount that gave us a fit. It seemed to cause more vibration than it absorbed. Knowing the mounts is #1. Some of these boats have the rear engine supports fastened to the Warner Transmission, others are fastened to the flywheel housing. Which do you have? Many DeFevers had our Heavy Duty Flywheel and D681 mount kits. I don't think you have this because of the vibration. Many times vibration is caused by a broken motor support (left front usually), loose motor mounts and uneven weight distribution from left to right. As a mechanic completes his propeller shaft alignment, he must feel the torque on the lower mount nut with a wrench, to assure that the mounts are carrying on all fours. Standing on one foot so to speak, it sort of amplifies the vibration. Don't under estimate the importance here! Now the engine itself can and does have a roughness. There are three smooth and rough speeds between 500 and 1000 rpm. It sounds stupid, but the thing to do is to find the smoothest speed on your engines and run them there. Idle speeds between 575 and 900 are many times found, as are tachometers which read a hundred or two off at idle. You pick the best speed then lock on it. By the way, the idle damper at the back of the pump is not the idle adjustment. The adjustment is on the inside- the upper screw (needs 13mm deep socket & screw driver to set) Adjust the idle damper after the speed is set. This is to take the roll or gallop from the engine after the speed is set. Note that clean and evenly set injector pressures are very important for smoothness! Lastly, your practice of running the engines will set the level of annoyance. Start the engines and idle them at 900 - 1000 speed for warm up until the lines are taken off and you get underway. The best warmup is underway below 1200rpm. We sell the Glendenning Synchronizer, which will practically eliminate the twin engine beat and vibration, even when warming up. This does more than anything else to smooth things out. See a boat which has one. It is the best $900.00 you will ever spend on your boat! That's enough for now, but you have some information to give me for the next step. Please tell me more so that I may be of help. Best regards, Bob Smith please reply to "bobsmithadc@juno.com" >Sent: 01/27 10:18 AM >Received: 01/27 7:15 AM >From: Randy Jacobs, ja447@ix.netcom.com >Reply-To: Trawler World List, trawler-world-list@samurai.com >To: Trawler World List, trawler-world-list@samurai.com > Does anyone have any good ideas as to how to eliminate or at least reduce the teeth shattering vibrations a Ford Lehman produces at idle? (700RPM) They smooth out completely at about 900-1000 RPM. Should I just set >the idle up and forget it, or what? The engine mounts are probably the originals (1978) but appear to be good. This problem is serious, my dental bills are astronomical! > >Randy Jacobs, ja447@ix.netcom.com >48' DeFever, ADIOS! >Port Clinton OH, (Soon to be Charleston SC)