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Old 22-12-2011, 15:53   #1
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Engine Alignment

I have been dreading engine alignment. Not sure why put it seems like a very precise type of movement of a heavy object (the engine) to get everything within tolerance. The job has recently leapfrogged to the top of my to do list because one of the engine mounts is in bad shape. The engine has almost 900 hours on it so I figure I might as well change all 4 of the mounts on my Yanmar 4JH4E. I have not found any DIY's of how to align the engine on this forum so thought I would start this thread and people with experience would maybe add to this knowledge base. As part of my homework I have read both Caulder's and Casey's description on how to do it. While surfing the net I found this video which has a lot of useful info. It is not about a sailboat but the theory is the same. I imagine that everyone's motor mounts are going to be different.
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Old 22-12-2011, 17:14   #2
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Re: Engine Alignment

Hello: I can only give you my limited personal experience, I aligned the engine with the shaft (translation) and then rotated the engine to get the rotational alignment all while the boat was sitting on shore. This was a great thing to do because it gave me practice, as soon as the boat went into the water I had to do it over again, but I then had experience.
For me it was just a question of patience to get it just how I wanted it.
Good luck and Merry Christmas.
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Old 22-12-2011, 18:01   #3
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Re: Engine Alignment

I think Casey did a good job in description. I rebuilt my engine bed and mounted all the engine mounts and engine while aligning the shaft. All I needed was a set of feeler gauges and the necessary wrenches to adjust the engine mounts. It takes a long time to do it right and you might have to go around to each engine mount several times to get it just the way you want it.
Good luck.
kind regards,
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Old 22-12-2011, 18:05   #4
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Re: Engine Alignment

Piece of cake. Take your time and recheck the coupler as you rotate it. If you mess up you just have to start over until it is right. You have plenty of good information. Don't accept "close", get it right. Chuck
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Old 22-12-2011, 18:07   #5
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Re: Engine Alignment

I've done two alignments - small Yanmar and large John Deere.

Both worked out well, though I'm not sure how much was due to good luck.

It must, of course, be done in the water.

The more time you spend preparing the better. In particular measure, measure, measure, then check your measurements and measure again.

If you can match your existing mounts in how they bolt to the engine beds and their size so much the better.

First step is to bolt the flexible coupling to either the gearbox output shaft or to the propeller coupling and to roughly align the engine.

Even if using a flexible coupling you'll need to get it all to within close tolerances.

Now the engine should be fairly close. Lay a steel ruler or other straight edge on top of the coupling and check that the alignment is close fore and aft. Repeat with the straight edge on the side of the coupling. If all looks OK then this could be a good time to bolt the mounts snugly to the engine beds.

Next I have put a light under the coupling and looked at it through the gap. It should be possible to see if the mating surfaces are parallel. If they are not then the engine mounts will have to move on the beds or the engine will have to move on the mounts. do this until the mating surfaces are parallel. This has been the tricky frustrating part for me as it is not easy to determine which mount needs adjustment. Best to do this when you are fresh.

Repeat with the light to one side.

Once the engine is roughly aligned loosely bolt the coupling together and follow the same procedure, but with a feeler gauge instead of the light. Rotating the coupling while putting light pressure on the feeler gauge will give some ides of how tight the it is in the gap. You need to have a sense of why it's called a "feeler" gauge.

Keep on going till the engine is aligned.

Now is a good time to go over the engine and to check that all bolts have been correctly tightened and everthing is in its correct place.

Don't drop the engine on your toe!
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Old 22-12-2011, 18:07   #6
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Re: Engine Alignment

If you can get your mind wrapped around the concept it isn't that hard, just time consuming.
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Old 22-12-2011, 18:22   #7
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Re: Engine Alignment

Quote:
Originally Posted by Boracay View Post


Even if using a flexible coupling you'll need to get it all to within close tolerances.
You really can not and should not try an alignment with a flexible coupler. To do it properly a spacer should be machined to fit the coupler and the alignment done with the spacer in place, and then the drive saver replaced when finished. Anyone that charges to do an alignment with a flex coupler is only taking your money. The drive saver will allow some misalignment but to do the job right require the spacer. Chuck
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Old 22-12-2011, 18:24   #8
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Re: Engine Alignment

In my case when I put to motor in I also replaced the shaft, coupling, mounts and shaft log. Couplings with shaft was all bolted up to the gear, then the motor with the mounts and drive train was aligned a close as possible to the opening in the keel, then the shaft log was aligned to the shaft, perfect and much easier than trying to align the coupling and motor to an installed shaft assembly.
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Old 22-12-2011, 18:40   #9
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Re: Engine Alignment

Removed and replaced my engin 20 years ago no prior experience,The concept is very very simple the shaft will only come in where it belongs all movement must be from the engin no short cuts two people are necessary one to move the engin one to keep checking the clearance between flange connection about 2 hours of playing with it and 20 yeasr later all ok,Do replace cutlass and repack stuffing box at this time.ps always check one last time after securing all the mounts making sure that last snugging of the bolts didn't move it some,
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Old 22-12-2011, 18:57   #10
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Re: Engine Alignment

Quote:
Originally Posted by Boracay View Post
I've done two alignments - small Yanmar and large John Deere.

Both worked out well, though I'm not sure how much was due to good luck.

It must, of course, be done in the water.

The more time you spend preparing the better. In particular measure, measure, measure, then check your measurements and measure again.

If you can match your existing mounts in how they bolt to the engine beds and their size so much the better.

First step is to bolt the flexible coupling to either the gearbox output shaft or to the propeller coupling and to roughly align the engine.

Even if using a flexible coupling you'll need to get it all to within close tolerances.

Now the engine should be fairly close. Lay a steel ruler or other straight edge on top of the coupling and check that the alignment is close fore and aft. Repeat with the straight edge on the side of the coupling. If all looks OK then this could be a good time to bolt the mounts snugly to the engine beds.

Next I have put a light under the coupling and looked at it through the gap. It should be possible to see if the mating surfaces are parallel. If they are not then the engine mounts will have to move on the beds or the engine will have to move on the mounts. do this until the mating surfaces are parallel. This has been the tricky frustrating part for me as it is not easy to determine which mount needs adjustment. Best to do this when you are fresh.

Repeat with the light to one side.

Once the engine is roughly aligned loosely bolt the coupling together and follow the same procedure, but with a feeler gauge instead of the light. Rotating the coupling while putting light pressure on the feeler gauge will give some ides of how tight the it is in the gap. You need to have a sense of why it's called a "feeler" gauge.

Keep on going till the engine is aligned.

Now is a good time to go over the engine and to check that all bolts have been correctly tightened and everthing is in its correct place.

Don't drop the engine on your toe!
Perfect! I often have used a drill bit butt end of any convenient size. (maybe .188) slip it in between the couplings and wiggle. Adjust the mounts until it has no wiggle in 3 or 4 equally spaced locations. I dont know why, just seems easier to deal with than the feeler gages... trying to determine the number of thousanths doesnt relate to the mount adjustment anyway I guess...
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Old 23-12-2011, 10:24   #11
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Re: Engine Alignment

Please keep the information coming. I will summarize some of the ideas that people have suggested.

1) Dectapper -- practiced on the hard and then redid it when in the water. Alignment must be done when in the water. Casey or Caulder recommended that a person wait 72 hours after the boat is splashed to give her time to settle into shape.

2) Skipper John -- Patience. You might have to adjust the motor mounts several times to get it right.

3) Waterway Guy -- Perseverance. Keep adjusting till it is right. I read on a website that a good mechanic can align an engine in an hour but a DIY mechanic may take up to 6 hours. (See engine alignment in this link One Week Yacht Engine Change)

4) Borcay -- Technique. Helpful ideas that I hadn't thought of were a) don't attach mounts to the bed till engine is roughly aligned. b) use a light to backlight the couplings to determine whether they are parallel or not. Adjust till parallel. and c) use a steel rule to align the couplings (assuming they are the same size) both on top and on the side.

5) Waterway Guy -- Have a spacer machined instead of using the flexible coupling.

6) Cburger -- On a new installation you can set the engine close and then adjust the shaft and coupler to it. (I would ask Cburger to clairify this because a change in the location of the shaft would require a change in the location of the log and the strut)

7)Casual -- Took two hours. Best to have two people. After the nuts are all snugged in place it is best to check the alignment one more time. Implied that the alignment has not been checked in 20 years. Is that true?

8) Cheechako -- Likes to use a drill bit rather then a feeler gauge. Adjust till there is no wiggle.

As part of my homework I am going to try and make up a chart with the effects of adjusting the different bolts. For instance -- If you adjust the rear bolts down this has the effect of moving the bottom face of the engine coupler away from the shaft coupler. If anyone know of such a chart it will save me reinventing the wheel. In "This Old Boat" Casey has a good description of the basics but I would like to get a better idea of what to do if the engine has a gap at 11 o'clock as opposed to 9 or 6. In other words (and this IS NOT TRUE) If the gap needs to be closed at 11 o'clock raise the starboard aft bolt 1/8 or a turn and the port forward bolt 1/8 of a turn.
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Old 23-12-2011, 10:37   #12
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Re: Engine Alignment

something to consider is the shaft log, whatever you want to call it, where the shaft runs into and exits the hull.
The shaft should be centered in the hull hole, or it could rub whatever you have. My boat uses a bronze shaft log which is clamped a rubber hose and clamped to this is the bronze packing gland. Mine had worn thru and almost would have started a good leak. I ended up building the worn area back with silver brazing.
Had to remove that part during a haul out.

You could in theory have the shaft just about right and the shaft will be touching this or too close. Then when the hull gets underway and is stressed, the shaft could rub the shaft log.
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Old 23-12-2011, 11:11   #13
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Re: Engine Alignment

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Originally Posted by Charlie View Post
I have been dreading engine alignment. Not sure why put it seems like a very precise type of movement of a heavy object (the engine) to get everything within tolerance. The job has recently leapfrogged to the top of my to do list because one of the engine mounts is in bad shape. The engine has almost 900 hours on it so I figure I might as well change all 4 of the mounts on my Yanmar 4JH4E. I have not found any DIY's of how to align the engine on this forum so thought I would start this thread and people with experience would maybe add to this knowledge base. As part of my homework I have read both Caulder's and Casey's description on how to do it. While surfing the net I found this video which has a lot of useful info. It is not about a sailboat but the theory is the same. I imagine that everyone's motor mounts are going to be different.
Is it essential to have a dozen smoking rednecks watch while you align the engine? That might be the biggest problem where I'm located.
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Old 23-12-2011, 12:38   #14
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Re: Engine Alignment

I will second a lot of the advice here. Go slow, take your time and have a second person to help.

A 2X4 about three feet long to use as a lever really helps making side-to-side adjustments. Make sure you protect the hull with another piece of wood.
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Old 26-12-2011, 14:35   #15
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Re: Engine Alignment

I've never done an engine alignment but have installed electric motors in various factories for pumps and such. In each case we used dial indicators clamped to the pump input shaft. We didn't have adjustable mounts most of the time, we used shims of various sizes, and there was some math involved in calculation of the shims.

For an engine install, I'd get the flexible coupling replaced with a machined spacer, then install a machined bushing on the inboard end of the shaft where it exits the shaft log. (this is if your shaft is only supported by the cutlass bearing) so the shaft is as immobile and centered as possible. You will also need to make sure that the shaft can't move forward or back. I would make up some sort of collar in two pieces that you can clamp onto the shaft in front of the bushing. Then you can clamp your dial indicator to the shaft and take the readings by either spinning the shaft or spinning the coupling. eventually you want to end up with all 0s on the indicator.

Start by seeing if the couplings are parallel. Take a reading at 12,3,6 and 9 o'clock on the face of the spacer. Once they are parallel you can check the offset and elevation. Take readings at 12,3,6 and 9 o'clock on the sides of the spacer. Ideally you will want 0 all the way around. By the readings you will know which way to shift the engine. Elevation is easy to fix, just adjust each mount by the same number of turns or fractions of turns. Offset is a tad more difficult as you must horse the engine from side to side in tiny increments without changing the alignment with the coupling. It will take a while. Save the beer for afterwards. Once the readings are all 0, take out the spacer, the clamp ring and bushing from the shaft log and replace the spacer with the flexcoupling and you are good to go.
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