Alignment after engine mount replacement

[smokey73]

I am replacing my Yanmar 4JH2E motor mounts and have a question.

I have taken all the bolts/nuts off for the transmission to shaft flange. It was separated about 1 year ago and the bolts came of easily. There is no apparent rust at the flanges. I have a PSS dripless seal.

I know I need to get a little space between the flange surfaces to allow movement/measuring the clearance. I can't seem to get the flanges to separate and move the shaft back a little. I don't know if it is because there is some kind of 'binding at the flange faces or if the spring force on the PSS diaphragm is holding the shaft forward. Any thoughts?

If anyone has had this problem or just know how to get the space so I can continue?

 

[dLj]

I am replacing my Yanmar 4JH2E motor mounts and have a question.

I have taken all the bolts/nuts off for the transmission to shaft flange. It was separated about 1 year ago and the bolts came of easily. There is no apparent rust at the flanges. I have a PSS dripless seal.

I know I need to get a little space between the flange surfaces to allow movement/measuring the clearance. I can't seem to get the flanges to separate and move the shaft back a little. I don't know if it is because there is some kind of 'binding at the flange faces or if the spring force on the PSS diaphragm is holding the shaft forward. Any thoughts?

If anyone has had this problem or just know how to get the space so I can continue?

Is the boat in the water or on land?

dj

 

[jssailem]

I suspect it is the PSS spring forcing the shaft towards the transmission coupling. If you can release the PSS collar on the shaft. Then slide the shaft back through the collar and PSS. That should open up the space at the coupler. If you are in the water, then releasing the collar will allow water to enter at the collar as the PSS graphite donut will not be compressed against the collar. Be sure your bilge pump is working. A rag wrapped about the PSS may help to stop the water from spraying in your face. Any compression of the PSS to stem the water will force the shaft up against the coupler transmission interface. You might have a diver stuff a plastic bag in the shaft log around the shaft to reduce the water flow. Your pump should be able to keep you afloat.

 

[marcham]

Don't forget to use new set screws if you release the PSS collar...

 

[Jan_H]

I'd try to tap a penknife blade in between the flanges to see if they separate, before you loosen the PSS collar. If they do, you could insert a 20 thou ring shim at one of the bolt hole locations, and use that as your reference to measure the space between the flanges.
Jan

 

[smokey73]

The boat is in the water. As @jssailem noted, I suspected it was the compression of the PSS diaphragm that was pushing the shaft forward. Since everything I read says the final alignment should be done with the boat in the water, I can't be the only person who is faced with this? Hoping someone who has done this alignment waterborne with a PSS shaft seal can chime in with the technique.

 

[smokey73]

Another interesting question.
With a PSS there is no restraining action like there is when you have a standard packing gland. The underlying assumption in aligning the transmission output flange to the shaft flange is that the shaft is already "in line" by being restrained by the shaft packing gland and the shaft cutlass bearing. In the case of a PSS, there is no restraining in the radial direction so the only thing holding the shaft in alignment is the cutlass bearing and that is not very long. I can imagine the shaft could be slightly out of line and pressing on the cutlass bearing.

Everything seemed to be in line before I started this so I made a "jig" out of wood that would position the shaft both vertically and horizontally as a starting point for when the shaft is aligned since I did not have any unusual vibration or noise at any rpm before I started this project.

Still, surely somebody with a PSS has aligned their engine and shaft while in the water. How do I assure the shaft is in alignment before I align the output flange to the shaft flange or is it wise to assume the shaft is aligned based only on the restraint provided by the shaft cutlass bearing?

 

[dmax]

When I aligned mine, I moved the collar forward just enough to relieve the pressure, leaked some but not that much, easy to clean up. It's very hard to determine that the shaft is centered in the log once the PSS is all assembled - I centered it on the hard (using 1/4" drill bits as spacers) and got everything aligned. Once in the water, the final adjustment was not that drastic, measuring seems to confirm the shaft is still centered. A wood jig could give more confidence. Engine is really smooth now and shaft is centered where it exits the log.

 

[dLj]

Sounds to me like you have things pretty much under control. Use your wooden frame to make sure the shaft is in correct position. Loosen up the PSS so you can move the shaft back a bit. Align engine and reset PSS. If you losen up just enough to slide the shaft back, you won't get much water in at all.

dj

 

[FastOlson]

Everything seemed to be in line before I started this so I made a "jig" out of wood that would position the shaft both vertically and horizontally as a starting point for when the shaft is aligned since I did not have any unusual vibration or noise at any rpm before I started this project.

Good Idea!
When we replaced our drive train in 2018, I found a way to lock the shaft in place and to keep the PSS seal compressed exactly as it was. Our alignment was already good for shaft alignment in the alley, so all we did was position the new engine to line up with it exactly.
I used an aluminum L angle bar across the area right in front of the PSS seal, and tightly clamped the shaft to it with a steel U bolt. Never 'leaked' a drop.
You can sorta see the solution in a photo from my blog. O34 - Old engine out, planning for the new one

True to the random-ness of advice from total strangers on the internet, I have a related answer for you, but not really the precise one you wanted...! You want an alignment, and what I have is a replacement of one...

 

[jssailem]

When we reinstalled my boat's shaft/transmission and engine, I was reminded that it would not be perfect.
It will be within tolerances.

We started on shore. The shaft was known to be straight and centered (mostly) in the shaft log. The shaft was tested to be true at the prop shop. The coupler was attached to the shaft and milled (fit and faced) to the shaft. It was centered and oriented at 90º to the shaft center. The shaft angle was at the prescribed angle for the engine block. With the shaft positioned, we located the engine/transmission on the mounts and slid the shaft towards the transmission. We then adjusted the engine to align with the shaft, correcting for offset and angular alignment.

With the engine and PSS set, we splashed the boat and, once in the slip, finalized the alignment.

I plan to run the transmission for about 15 hours, then check the alignment and make any corrections to the engine mounts. So far, observations show no unusual vibration or wobble while the shaft rotates. The boat is in the slip.

After several in-slip tests I took the boat out of the marina and ran it at various speeds and maneuvers. There were no anomalies observed.

 

[sesmith]

No need to loosen the pss. I would tap on the side of the coupling in a couple of places with a brass hammer to make sure it isn't stuck together and rotate the shaft a few times and rock the motor to make sure the connection is loose. Then measure with your gauge. The pss seal pressure actually makes measuring the gap easier as it keeps pressure on the flange and you're only then measuring any gap caused by misalignment.

 

[smokey73]

OK, got the engine alignment done and it looks very good to me. Less "wobble" than before.

HOWEVER: As I was concerned about, I am pretty sure the shaft/engine, although aligned, the shaft is not centered in the strut bearing. I feel this is the case (I'd say "know" but I'm asking for input.) When I push down on the black carbon ring of the PSS it is hard against the shaft and will not move at all. When I pull up from the bottom of the carbon ring, there is a pretty good amount of movement and water comes out the joint between the carbon ring and the rotating steel collar. Also, I can turn the shaft by hand in neutral, but it is not easy.

Would you agree with the following? I need to lower the whole engine/shaft a little by adjusting the motor mounts in such a way as to maintain the alignment. In doing so I need to devise a way to keep the alignment geometry. By that, I mean if I only adjust the back motor mounts to lower the engine it will put a bending stress on the shaft. So any adjustment in the motor mounts have to be to both the rear and front mounts is some ratio so as to keep the shaft and engine aligned with the shaft.

As an alternative, I guess I could disconnect the shaft flange from the transmission flange. attempt to align the shaft in place so that there is minimal effort necessary to rotate the now free shaft. That should indicate when the shaft is centered in the strut bearing. I'll need to then fix the shaft someway so it does not move and then reperform the alignment.

In the long run, it seems the latter may be the best approach. What think you?

 

[Rich Stidger]

@smokey73 -
If I were a carpenter with a hammer, every problem would look like a nail. But since I am an engineer (or was), I am going to offer you an engineering solution. Warning: This might be over-thinked......

I understand that your problem is to drop the engine while keeping the same angle to the shaft. You are happy with the thwart-ship alignment.

So thinking about range marks for entering a channel, I suggest the following:

Cut a cardboard box, removing the top and a window in one side. Tape a clear piece of plastic over the window. In the picture below I used a small sandwich storage bag, but if I were to do this for real, I would use a piece of clear Vue-Graph slide for an over-head projector. It is stiff and clear enough to work well.

Then secure the box on your aft berth so that it cannot move at all. Use a laser pointer that is secured to the engine. Use clay and or duct tape to secure the pointer tightly and aim the pointer through the Vue-Graph window so that it hits on the backside of the box.

MARK the spots on the Vue-Graph and on the back of the box where the laser pointer hits.

Now you have a range-mark setup. If you adjust the front and rear mounts equally you can lower the engine to your satisfaction. As you lower the engine, make sure that the distance dropped on the Vue-Graph sheet and the cardboard box remain equal. This technique will let you lower the engine and yet keep the same angle with the driveshaft.

I made up a test box and have attached a couple of pictures to help illustrate the setup.

 

[heritage]

I agree that you need to lower the engine and attempt to keep it in alignment with the drive shaft as you lower all four mounts. My guess is that even with great care, the odds of it setting into perfect alignment are very slim. So you will more than likely need to decouple the shaft and transmission and make final adjustments.

 

[smokey73]

I agree that you need to lower the engine and attempt to keep it in alignment with the drive shaft as you lower all four mounts. My guess is that even with great care, the odds of it setting into perfect alignment are very slim. So you will more than likely need to decouple the shaft and transmission and make final adjustments.

My thoughts too. I'll probably try to lower the engine as best as can to get the shaft in alignment with the stern tube and strut, then decouple the engine to let things settle out and proceed with a final alignment. I'll need to rig some sort of jig to hold the shaft in place during the alignment

 

[sesmith]

It is a tricky thing to try and do in the water, but you need to have the shaft centered in the shaft log and then do the engine alignment matching the engine to the centered shaft. Ideally, you would wedge the shaft centered in the shaft log but that can't be done with a pss seal in place. I've always done my engine alignment first out of the water, so I can see that the shaft is centered from below the boat (but that depends on how the shaft exits the boat). I guess you could swim to check this. Then align the motor. Then I always recheck it after a couple of weeks in the water, but all it ever needed was a slight tweak up or down.

Note that it's really easy to chase the alignment with feeler gauges only to find that you've walked the shaft onto the side of the shaft log.

 

[jssailem]

Thinking about your situation. You followed the normal process of alignment. Then testing the free rotation of the shaft you find friction where you expect smooth rotation. Assessment the shaft is binding on the cutlass bearing, so I must lower the engine. Ok.
Did the shaft rotate freely before it was connected to the transmission?

I’m wondering if this is a new expectation or discovery that the alignment needs tweaking. If not sure then, I would release the bolts on the coupler and check the shaft rotation. You are pretty sure that the current engine/transmission setting is In alignment. If you can freely rotate the shaft after release then you need to further adjust the engine/transmission setting. If the shaft does not rotate freely by hand then the assumption that it should when coupled is false.

My logic is that instead of assuming misalignment that when in place there is resistance of the cutlass bearing and shaft. When in rotation water gets introduced and serves to lubricate the interface.

 

[smokey73]

Thinking about your situation. You followed the normal process of alignment. Then testing the free rotation of the shaft you find friction where you expect smooth rotation. Assessment the shaft is binding on the cutlass bearing, so I must lower the engine. Ok.
Did the shaft rotate freely before it was connected to the transmission?

My assumption is based on a couple things.
1. When I push down on the PSS carbon ring, it is readily apparent that the shaft is too high by about 1/4 inch or so at the ring. There is no movement at all when I push down (it is hard up, as we say in the Navy) but there is about 1/2 inch movement when I pull up on the carbon ring. It always was, and should be now, about centered in the carbon ring.
2. After my last post, I lowered the engine "just a tad" and the shaft, while not exactly easy to rotate, was easier after the small amount of lowering which seems to confirm my assumption. The shaft is still not centered in the carbon ring yet though.

I'll disconnect the shaft from the transmission today and see if small changes in position of the shaft make it easier to rotate. Without a packing gland, the shaft should be pretty easy to rotate while the boat is in the water. I have to disconnect anyway since I have already messed with the engine alignment by lowering it just a little bit. I'll report back in when I get this sorted.

 

[jssailem]

Reasonable approach. The carbon ring introduces an additional variable. When the coupler is disconnected you reduce the variables.

When shaft is rotating smoothly, centered in ring ( and shaft log), then sighting the center of the coupler and the shaft should give you engine/transmission height setting.
Fingers crossed.
Never worried about engine shaft alignment on the planes. When the mechanics screwed up the prop took off on its own. I was in the shop with the tech gear when they did engine testing. It went smoothly or there was a lot of noise. That meant someone was having a bad day.