Engine Alignment

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J

Jim Grant

How often should my engine be aligned? Has anyone done this on their own? Is it covered in the manual?
 
G

Gordon Torresen

If everything stays tight and the hull doesn't change shape, you may never have to adjust your alignment. However, it should be checked periodically. If the boat is put in a cradle for any length of time, the hull could move and affect engine alignment. The alignment should be checked a few weeks after the boat has been afloat for a few weeks in case the cradle deformation goes away. To check the alignment, you disconnect the coupling halves by removing four bolts. You then move the shaft to seperate the halves enough to permit movement of the shaft. Be sure that you are not leaning on the engine when making any checks or measurements. You then move the shaft radially up and down and then sideways until you feel the shaft hit the inside of the tube that is inside the stuffing box. From this motion you estimate where the center of all the motion is. This will locate the shaft with respect to the cutless bearing and the stern tube. This position should line the shaft up with the output of the engine. If it doesn't, you have to start relocating the engine. Keep in mind that the position of the shaft is fixed by the geometry of the boat and the engine must be aligned to it. There are slots in the base of the mounts to allow for lateral movement and adjusting screws at the top for the vertical. Once the engine coupling half is in the same position as the shaft half you have to start the angular alignment. First bring the two halves together and measure the distance between the faces at several places. Then rotate the shaft half a turn and check again. You will probably get different readings but if the widest measurement is not in the same radial position, you have misalignment between the shaft and the coupling half and the only way to correct this is to pull the shaft and make corrections to regain perpendicularity between the shaft and the face of the coupling. If the two faces run true, you then adjust the engine to get an equal reading between the faces, all the way around. We generally adjust until there is no more than .003" difference. You must keep in mind while making the angular correction that any movement of the engine, up or down, left or right, moves the position of the output shaft requiring the the whole engine must again be moved to get the couplings on the same centerline. Checking is easy. Readjusting is difficult and sometimes time consuming. A good marine mechanic has made this adjustment many times. An individual who is mechanically inclined and who has a long attention span can do it for the first time. If you are seeking to correct vibration, the flange half faces are not in the same plane. There are no adjustments to correct this. If the flanges do run true, misalignment will NOT cause vibration. It may rub a hole in the stern tube or cause excess wear at the cutless bearing but it will not make the system vibrate.
 
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