23 Sep Engine Alignment (a.k.a ‘shaft alignment’) Tips
One of the most commonly overlooked issues on inboard marine engines is called “Engine Alignment” (aka Shaft Alignment). It’s one of the most critical issues to premature wear in the engine, transmission, and drivetrain underneath.
The most common symptom of misalignment is a vibration in the deck as speed increases. (This is assuming you have already inspected the prop for a bent blade.) Shaft Alignments MUST be done in the water so the hull is in it’s natural shape.
Here are the steps to perform a proper engine alignment. (After you read all of this you will understand why it “never gets done.”) Call us! We will gladly do the job for you saving you thousands in the long run!
You will need a set of “Feeler Gauges” straight style as if to adjust valves, a hammer (ball peen and even a brass hammer would be best if you can get one).
1. With a scribe, blade etc. draw a line across the two halves of the coupler to make “timing marks.”
2. Disconnect the two halves and separate them.
Get your base alignment correct and most importantly make sure the shaft is as close to the middle of the shaftlog hole as possible. Do this by feeling the play in the shaft, as if the shaft is sitting on the bottom of the log, undo wear and tear on the stuffing box, and noise will prevail. If this is correct then when you go to step 3 you will actually have to “lift” the shaft a minor amount to mate the halves.
3. Without using the bolts, slide the shaft and reconnect the two halves––lining up the marks you made. While keeping pressure from behind, tap the coupler from behind with a hammer. (NOT HARD just firm.)
4. Using a .003″ (three one thousandths of an inch) feeler gauge, run it all the way around the “seam” where the two couplers join. The feeler gauge should not drop in between the two halves if the alignment is correct. If it drops in the sides, your side to side is out, Bottom, then either lower the front or raise the back. (You get the idea.) Remember there are two adjustments for each mount. Side/Side and top/bottom.
5. When making adjustments, make only ONE adjustment at a time. Tighten it down completely and then recheck. Never make two adjustments, because if you have to backtrack, then you won’t have a clue as to how to get back to “ground zero.”
After you make each adjustment, redo steps 1-4. This is a long tedious process, but the payoff is no vibration once you get it right. Plan on taking 1/2 to 1 full day to do this correctly as it is a slow process. After you do this, you should repeat the process after 20 hrs. (It will go much quicker as you will only have to make minor adjustments.) Then repeat once a year after re-launching and running an hour or so (again to reshape the hull).
Take care of your boat and you will enjoy it much more.
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