A few questions about prop shaft alignment

[Project_Mayhem]

I've done a little bit of research and have a general idea of how to align a shaft. I got a new shaft and coupler before the beginning of last season. I believe there's more vibrations that normal. This year I installed a PSS seal. The boat is on the hard still.

• I saw a video that started out by aligning the shaft with the rough center of the log. It sounds like a good idea but are all logs centered to the strut?
• Since my boat is on the hard, should I bother with alignment or wait? I have a five hour journey to my slip. Technically I'm only supposed to be in the yard's slip for a couple of days after launch but can likely request or pay for a couple more. It usually takes me a few windy sails to get the rigging tightened
• Will the PSS seal help push the couplings together or make aligning more difficult?
• How does one know if the front or rear of the engine needs to be adjusted?
• Do you tap or push the couplers together during alignment?
• If the engine needs to be moved laterally, what's the best method on a sailboat? A prybar seems to be the way to do it on a motorboat

 

[jssailem]

• I saw a video that started out by aligning the shaft with the rough center of the log. It sounds like a good idea but are all logs centered to the strut?
  • Logs are generally in line with the strut when installed. If the strut is replaced it is supposed to be in line, centered, with the shaft log. A laser shot through the center of the strut cutlass bearing to the transmission hub is a good tool.
• Since my boat is on the hard, should I bother with alignment or wait?
  • There are two alignments: First to get the general set up with prop shaft centered and connected to the transmission. I hope you had the new shaft and coupler “fitted and faced”. This sets up the basic alignment while on the hard. It is when you are doing the needed rough alignment of the engine.
  • The. Second is when the boat is in the water for a period (I like 24 hours). This gives the hull time to adjust to the water pressure and regain it’s shape. Then I preform the final adjustment to spec. Should only be minor adjestments no need for a crowbar.
• I have a five hour journey to my slip. Technically I'm only supposed to be in the yard's slip for a couple of days after launch but can likely request or pay for a couple more. It usually takes me a few windy sails to get the rigging tightened
  • I’d prefer to do the final alignment before going on a 5 hour cruise.
• Will the PSS seal help push the couplings together or make aligning more difficult?
  • Should not be a factor. You are aligning the center of the strut with the transmission side of the coupler. This should put the shaft in the near center of the shaft log. The PSS seal rides along the structure.
• How does one know if the front or rear of the engine needs to be adjusted?
  • Follow the spec. You use feeler gauges to identify which side of the coupler needs to be adjusted. You then halve the value and adjust left or right up or down as indicated. Then check again. If you go the wrong way revers what you did.
• Do you tap or push the couplers together during alignment?
  • On my boat th mechanic and I just slid the shaft into the boat. We placed the engine on the mounts. Roughly centered on the shaft using the laser as a guide. I grabbed the prop and pushed it inward till he told me to stop. He aligned the holes and secured the bolts. This snugged up the to halves of the coupler.
• If the engine needs to be moved laterally, what's the best method on a sailboat? A prybar seems to be the way to do it on a motorboat
  • A pry bar seems a bit much and may damage the fiberglass stringers. I have heard that inflating a basket ball can be effective. I have also see these air inflates that are used in cabinet and door installations They look like a decent tool that could be applied to a boat.

Check out the post @Ralph Johnstone did on engine alignment. As I recall it was very good.

Just my thoughts on the task.

 

[dLj]

One of my favorite tools for aligning is a Starrett No. 270. It's a tapered feeler gauge. I don't think they still make it but I'm sure you can find one used.

dj

 

[Barnacle Bill]

Another way of checking shaft alignment is to use a "dial gauge". It is a contraption that has a foot that rests on the shaft and the foot is attached to the gauge. When the shaft turns, if it is out of alignment, then you will see how much on the gauge. It is a cool contraption. Imagine your finger resting on the shaft and as it turns, your finger would go up and down rapidly consistent with the misalignment of the shaft. Most boat owners don't have such an animal, but maybe a marina technician will and he can check it or lend it to you.

 

[Tally Ho]

I did an alignment on the hard when I replaced my shaft and coupling. Then I re-checked after the boat was in the water.

Greg

 

[dLj]

Another way of checking shaft alignment is to use a "dial gauge". It is a contraption that has a foot that rests on the shaft and the foot is attached to the gauge. When the shaft turns, if it is out of alignment, then you will see how much on the gauge. It is a cool contraption. Imagine your finger resting on the shaft and as it turns, your finger would go up and down rapidly consistent with the misalignment of the shaft. Most boat owners don't have such an animal, but maybe a marina technician will and he can check it or lend it to you.

I'm not understanding how one uses a dial gauge for shaft alignment. I use dial gauges to check for shaft straightness if the shaft is mounted in a lathe. I don't understand how it would be used to check alignment between the flange on the engine to flange on the shaft. Perhaps you can explain more?

dj

 

[Ralph Johnstone]

I don't understand how it would be used to check alignment between the flange on the engine to flange on the shaft.

Same here. I think that's about all you get .................. is each flange true to its own shaft ? I can't see how that works when comparing the two flanges to each other.

One of my favorite tools for aligning is a Starrett No. 270

I'd kill to get my hands on one of those. I checked Amazon and all you get is the lying bastards who throw the word "tapered" into their cheap advert. babble. Same old feeler gauge with the crumpled up blades.

 

[Ralph Johnstone]

Then I re-checked after the boat was in the water.

Was there much change after it was in the water.

 

[dLj]

Same here. I think that's about all you get .................. is each flange true to its own shaft ? I can't see how that works when comparing the two flanges to each other.

Yeah, I can't visualize it. But hey - I'm always open to learning new tricks...

I'd kill to get my hands on one of those. I checked Amazon and all you get is the lying bastards who throw the word "tapered" into their cheap advert. babble. Same old feeler gauge with the crumpled up blades.


View attachment 237239

It turns out Starrett apparently does still make them. I thought I'd looked a few years ago and couldn't find them on Starrett's list of available products, but I just found it. However, the price for one from Starrett has a pucker factor attached... But if somebody is doing this work frequently, it is well worth the price.

I've had mine for many years, I'm not sure, like maybe 30 or more? In my last job we had a calibration lab that was right next to my desk so I took mine in one day just to see if it was even close to still in calibration - surprisingly it was. Now that was probably 10 years ago so it's certainly not considered "in cal" right at the moment but it sure gave me a nice warm fuzzy feeling. Not that that really matters for doing this kind of alignment work as you really only need a comparative measurement. It makes more of a difference if using it to measure for adding in shim stock - the reason I originally got it.

dj

 

[Rich Stidger]

Another way of checking shaft alignment is to use a "dial gauge". It is a contraption that has a foot that rests on the shaft and the foot is attached to the gauge. When the shaft turns, if it is out of alignment, then you will see how much on the gauge. It is a cool contraption. Imagine your finger resting on the shaft and as it turns, your finger would go up and down rapidly consistent with the misalignment of the shaft. Most boat owners don't have such an animal, but maybe a marina technician will and he can check it or lend it to you.

I would also like pictures and a description exactly on the use of a dial gauge. I have one so I just need the mechanics of the process.

 

[Ralph Johnstone]

Why must you people keep posting this click bait ? I can't get nuttin' done around here if I keep getting these interruptions.

Your annoyances even got me to look back at the earlier post #4 which started this tempest in a teapot.

It is a contraption that has a foot that rests on the shaft and the foot is attached to the gauge.

You want it on the perimeter of the prop shaft flange and then the flange face. The shaft may be true but the flange may be cocked which you would miss if you only checked the shaft.

 

[FastOlson]

Something like this?: https://www.harborfreight.com/1-in-...MIjIKzs7jmkwMVeQetBh3BtDO3EAQYAiABEgLjF_D_BwE

 

[dLj]

Something like this?: https://www.harborfreight.com/1-in-...MIjIKzs7jmkwMVeQetBh3BtDO3EAQYAiABEgLjF_D_BwE

Yes, that's an example of a dial gauge. I have several. I have one that is an order of magnitud more precise that this one you linked to - they come in a number of forms. I'm not visualizing how one would use that kind of gauge to measure the space between the engine flange and the propeller flange.

You need the propeller shaft to be both centered with the engine shaft and the flanges parallel to each other.
That's usually done with feeler gauges placed between the two faces at various locations around the flanges.

I believe the document that has been mentioned is attached.

dj

 

[Tally Ho]

Was there much change after it was in the water.

Not much. I was surprised.

 

[High Current]

I didn’t have to do side-side which helped a lot.

It was easy to push the coupler together by hand: I then used my thinnest feeler gauge to confirm that at least one point on the coupler had no gap.

From there some measurements and trigonometry helped a lot. By knowing the coupler diameter and the distance between the front and back mounts you can calculate how much to raise/lower the front to correct the angle. This also moves the tail up/down, based on the angular change and the distance from the aft mounts to the coupler. If you know (or measure) the turns per inch on the mounting bolts you can convert these distances into number of turns: X on the front two to correct the angle plus Y on all four to correct the up-down movement of the coupler that results from making the X adjustment. I only needed to make two total adjustments to get mine near perfect - quick and easy!

While still on the hard, make sure the shaft runs straight through the center of the shaft log and move the engine as needed to center it before starting the angular alignment process described above. This is important for your PSS as well as, in extreme cases, preventing damage from the shaft contacting the log.

 

[Rich Stidger]

While still on the hard, make sure the shaft runs straight through the center of the shaft log and move the engine as needed to center it before starting the angular alignment process described above. This is important for your PSS as well as, in extreme cases, preventing damage from the shaft contacting the log.

How do you determine that the shaft is centered in shaft log? If the flange is disconnected, the shaft will droop. What you really need to achieve is that the shaft is running through the center of the strut and the log. The problem is how do you measure this alignment?

 

[Ralph Johnstone]

I would also like pictures and a description exactly on the use of a dial gauge.

The dial indicator is used to check the trueness of the two flanges to their respective shafts. And that's as far as you will get. Unfortunately, checking the alignment of the two shafts to each other is not possible using a dial indicator.

Picture in example A) that you can get a dial indicator and firstly anchor the base of the indicator to something nearby that is rock solid. Then place the pin of the indicator touching the Xmission flange face and slowly rotate the Xmission flange. If the needle on the indicator doesn't wobble, you know the flange is true on its shaft.

Now what about the shaft itself coming out of the Xmission ? Swing the base of the indicator around to something rock solid again and now put the needle of the indicator against the outside perimeter of the Xmission flange. If the needle doesn't wobble, the Xmission shaft is true and the shaft and its flange are true to each other.

Oh crap, I can't explain this without waving my arms all over the place so I went down to the workshop and dragged out the dial indicator and photographed it in place.

Here it is by itself ready to measure anything that isn't moving :

The base (magnetic block) isn't firmly anchored yet. Mount it anyway you can using 2X4's nailed to whatever or a steel plate held onto something with a C-clamp. The only limit is your imagination. The magnet (when engaged) is pulling somewhere well north of 50 lbs. I couldn't lift it off the bed of the tablesaw but then again, it doesn't have much in the way of handles.

Here is the gauge ready to measure the damage I did to the wheel on my bike the last time I was out riding :

The measurement pin is at a right angle to the plane of the wheel. If the wheel is misaligned with the shaft the indicator will wobble. Considering the speed of the bike and the size of the boulders I was bouncing off, yeah, I'd bet good money on it.

If we could measure the wobble at the perimeter of the wheel (tire tread ), we would be looking at the the possibility of a bent axle causing any deflection on the gauge. In actuality, the bicycle wheel could be mangled to the point where it would be bouncing every which way at once due to the light weight construction of the wheel. The prop shaft and its flange are far more rigid and would therefore adhere to the rules of deflection far more tightly.

Those are the two preliminary measurements you are looking at taking on your prop shat anf Xmission shaft. If they are both true, you never need measure them again unless you start shifting heavy rocks with your prop. That could possibly bend your shaft and break the budget.

 

[CYQK]

Ok..because you have the PSS seal you will be better served by starting the alignment process on the hard.

The reason for this is you should do the alignment before you set the bellows pressure on the PSS seal
Keep the seal loose and use your feeler gauges to do your alignment

Start with a larger gauge do your primary alignment then switch to the smallest thickness and do a finish alignment . Works better this way!!

 

[FastOlson]

Perhaps worth a mention is to carefully check the shaft before re-mounting it in the boat. I recall that the owner (50 years) of a local shaft and prop shop used to tell us that he would check every single (!) shaft for true-ness after it came off the storage racks and before it was machined for the install. He said that just resting on the rack for a number of months would/could cause a slight "sag" only discernible with a gauge. His shop had a top notch rep. for quality work.

 

[dLj]

Perhaps worth a mention is to carefully check the shaft before re-mounting it in the boat. I recall that the owner (50 years) of a local shaft and prop shop used to tell us that he would check every single (!) shaft for true-ness after it came off the storage racks and before it was machined for the install. He said that just resting on the rack for a number of months would/could cause a slight "sag" only discernible with a gauge. His shop had a top notch rep. for quality work.

That's an interesting comment. I've got to wrap my head around that one...

I will add, that all storage I've used for shafts like this have solid shelves so there is no point of suspension per se...

dj