Shaft Alignment Question

Hey All! I have my prop off for pitching/polishing and am thinking this would be a great time to "ballpark" align the shaft without the additional prop weight. I've never done it before. Here's where I'm running into myself: the shaft is currently supported through it's 15 ft. run by two (ancient) pillow block bearings. I'm thinking these would need to be removed before I align the shaft. Once aligned, how do I get the bearings right with the shaft and each other? The shaft runs slightly downward and the bearings (see enclosed pix) would need to be aligned to the shaft and each other. *Any iseas/suggestions would be most appreciated. Thanks!

I'm in with Carl on this one. If it ain't broke... * Just grease your pillow blocks and keep on cruising.

Yes I agree that you shouldn't dick with it but I only see the one yellow pillow block bearing.
The other looks like the shaft coupling attaching to the tranny.

I'll join the other non experts in expressing the opinion that you should leave it alone unless you have some reason to believe it is out of alignment.

However, if you do want to fiddle, I don't think the pillow blocks are meant to be part of the alignment process.* I doubt they are needed for support except when the shaft is turning, and then they would keep it from oscillating.* They would have been put onto the shaft without attachment to stringers, and shimmed so as not to put any stress at all on the shaft when bolted down and secured.

If you want to test them, cast them loose from the stringers, align the shaft as normal, and then see if they can be reinstalled without introducing any deflection the shaft itself. You should be able to slip the base of the block under the shaft without pounding it into place.* You should also be able to bolt the top onto the base without deflecting the shaft.* If these are both true, you should be good to go.* If not, shim the base up or machine the shim you have down to it fits together without placing any stress on the shaft.

Does that make sense?

Old Stone wrote:

Kev - I am no expert (or even lowly novice) at this, but if you have no vibrations, and no looseness in your bearings, and you haven't hit anything, why would you want to open a can of worms ? Make any sense ?

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*********I agree with Carl, and the others.****

********

Just for fun... I'll say this... "If it ain't broke, take it apart and break it so it needs fixing."

The rubber in the engine mounts can soften over time. The motor then tries to twist or tip*and the prop-shaft tries to prevent this happening.

If you want to explore this possibility, unbolt the shaft/gearbox flange joint (coupling) and slide the shaft backwards a tad until*there is daylight between*the two halves of the coupling. Now check if the flange faces are still in alignment (parallel and sharing a*common axis).*If there is mis-alignment, then the engine must be moved*to correct it. You might then consider renewing the engine mounts. Good luck.

-- Edited by Shoalwaters on Monday 21st of March 2011 05:23:15 PM

Thanks Guys - I've been reading that I should do the alignment drill every year, so thats why I was going to get into it. Vibration isn't currently a problem. It would be great if I could postpone this one for awhile, as there a ton of other projects to get after when the snow finally goes(It is snowing right now 3/21/2011!) -

BelfastCruiser wrote:

Thanks Guys - I've been reading that I should do the alignment drill every year, so thats why I was going to get into it.

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Alignment is not typically a preventative maintenance item.* It should be based on need, assuming you are paying attentive to vibration.* It would*make sense to do it with a new-to-you boat to establish a base line level of vibration related to proper alignment.

So far in almost 14 years, have aligned the shaft twice, once after putting in a new shaft, and once after putting in new engine mounts/drive plate.

When the intermediate shaft bearing finally dies , you will need to remove it from the shaft , probably by pulling the shaft.

Purchase a marine servicable unit and you will be able to replace the roller bearings in place.


Takes about 15 min and your good as new.

May save your butt if you go cruising.

To check the alignment of the prop end of the shaft is to turn the shaft and see if there is any movement up or down, and/or measure along the shaft for movement.* You can buy measuring gauges at Harbor freight for 20 bucks.* *Also a 15 ft SS shaft which is slow turning, 500 to 800 PRM, could be out up to 10+/thousand from end to end as they tend to shag over time, which is what the bearing block is for.*It is recommend if stored for long periods of time to move/roatate a long shafts.*** Also if it does move it might be the shaft not the alignment.* So the shaft should be check first.*Also alignemnt should be done with the boat in*the water for about a week to let things settle.



I recommend you take the shaft to local machine shop and not to a prop shop to get the real story.* If the shaft need to be straighten, they can should be able to straighten or tell you where to have straighten, which will take less than a hour, about 100 bucks.* Anyway before you mess with it, do some measuring first and then if there movement then talk to a local machine shop.* My 12 ft shaft is probable out 10+/thousand from end to end but the ends are right on.*-- Edited by Phil Fill on Tuesday 22nd of March 2011 10:43:14 AM


-- Edited by Phil Fill on Tuesday 22nd of March 2011 10:45:47 AM

Jay wrote:
"Alignment is not typically a preventative maintenance item." I disagree. Not strongly unless there's a vibration problem.
A boat can't be blocked up such that it's supported as it is in the water and if unskilled people do it the keel could be hogged or otherwise and the hull could be twisted.
Alignment should'nt be attempted until the boat has been launched for a few days.
Carl wrote:
" I don't think the pillow blocks are meant to be part of the alignment process." I agree Carl but like a wood boat (but much less so) a FG hull can/does warp over time and pillow block shafts should be checked and corrected if needed.
Shoalwaters wrote:
"The rubber in the engine mounts can soften over time." Very good point and they should be replaced now and then. Yanmar recommended replacing their mounts annually but I think that's extreme. Oil, heat and other things break down rubber engine mounts so they do sorta wear out and many/most engine installations don't have mounts that are evenly loaded so alignment should be done at times. Those times should be when miss-alignment is detected.
BelfastCruiser, I would wait until you're back in the water but it may be interesting to check your alignment at the gear/shaft coupling while you're on the hard and see the difference in the water. Later I would use wood pry sticks to lever the shafts up or down to see how much play or slop there is in the bearing to shaft fit. Jack up the engine with the engine mount adjusters untill both pillow block brngs are above thier mounting surface. Then lower the engine until one of the PB brngs contacted it's mounting surface. Secure that PB bearing. Then shim up the other PB brng to match. Then go through propper engine to Prop shaft alignment in all three axis. Then you're done. However all the above does not insure alignment of the shaft in the stern berng but it should be extremely close if the after-most PB brng is very close to the same position as before or as original. Something else to think about (if this thread is'nt enough) is that if there is quite a bit of wear in the PB brngs the shaft may rattle in the brngs. Your shaft is probably worn and not straight. There is no such thing as a straight shaft. I worked in a machine shop that made propeller shafts for boats and all new shafting was "straightened" during the process of making the shaft. They beat on the new shaft to get it as straight as time would allow. You could save the old shaft by installing a flexable shaft coupling or "Shaft Saver" that would normally require you to cut off some of the shaft and then re-cut the taper and retainer nut threads. One last thing. A 15' shaft supported only at both ends will droop If you attempt to align the shaft straight there will be a load on the pillow block brngs that will (in my opinion) wear the shaft/brngs prematurely. About this last issue I could be wrong but I think not. The PB brngs are only to limit the shaft's tendency to move around radilally. Dan Peace and I have been talking about the dangers of turning the pillow block brngs into thrust bearings when using ball brng PB brngs since the inner race should be fixed to the shaft w a set screw. Haven't sorted that out yet*** ....any comments?



-- Edited by nomadwilly on Tuesday 22nd of March 2011 11:33:51 AM

"Dan Peace and I have been talking about the dangers of turning the pillow block brngs into thrust bearings when using ball brng PB brngs since the inner race should be fixed to the shaft w a set screw. Haven't sorted that out yet*** ....any comments"

My "ex" boat was an old Mainship 34. They all had a ball bearing "pillow block" style mid shaft bearing.
Shafts were 103" long and this bearing was attached to one of the bulkheads. The bearing was a Torrington/Fafnir *RCJC style (either 1 1/2 or 1 3/8) and yes the inner race was set screwed to the shaft. Apparently the bearings could handle what little thrust load they saw as they would literally last years.


Here's a maintenance tip to consider no matter what the bearing...add an automatic grease cup to automatically grease the bearing.*Esp if the bearing is*difficult to access as it was in the Mainships. *Use a length of hyraulic hose to put the grease cup where it's easy to monitor and refill.

-- Edited by jleonard on Tuesday 22nd of March 2011 12:51:27 PM

Jay,
Can you tell me why they wouldn't recieve 100% of the load?

nomadwilly wrote:

Jay,
Can you tell me why they wouldn't recieve 100% of the load?

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Doesn't the tranny take the brunt of the thrust load?

Takes 100%

BUT if one has an intermediate ball bearing that has it's inner race fixed firmly to the prop shaft via a set screw then it would seem to me that the intermediate berng will take all the thrust and I know that's not the way it should be. The thrust berngs in the gear box are designed for that purpose. Ball berngs have very limited thrust capability. With BelfastCruiser's boat it looks like he's got plain berngs and they take no thrust at all so the thrust is delivered (as it should be) to the gear box. When one goes from reverse at 75% to fwd at 75% the engine moves fore and aft about 1/16" (rarely that little) to 3/8". Boats that have intermediate brngs either have a set screw that just gouges the shaft or the set screw actually works and the intermediate berng is then taking 100% of the thrust load both fwd and reverse. It looks like there's a lot of people installing prop shafts that don't know what ther'e doing. More than likely I just don't understand the installation. Again, I'm not really sure about this.

Depending on the tranny , some will move the output flange fore or aft about 3/8 of an inch, with szelection of FWD or REV.

Since the tranny in most cases is the thrust bearing this must be accounted for if a pillow block is used.


-- Edited by FF on Wednesday 23rd of March 2011 04:57:40 AM

Eric, I don't have a real good answer. Every 1977 thru 1987 Mainship 34 had the same mid bearing setup as OEM.

I am not sure if the oiriginal bearing was installed properly, but when I put in the new Aquamet shaft ahead of*my repower I installed my second new bearing (only because I had everything apart and I worked for Torrington Co and the bearings were free) I made the proper drill spots for the set screws. My bearing actually had 2 setscrews and they both got spotted.

If the thrust load was transferred to the bearing then it must have been up to the task although I know it was not designed for thrust loading.

A suggestion from National Fisherman.

Run the engine out of gear and find a nice smooth "sweet spot" note the RPM.

Put the engine in gear and run it at that RPM.

Any noise or vibration is from the drive train.

Hey I like that one FF. Don't think it's bullet proof though. A bulkhead could be resonate to a givin eng speed but wo a load on the eng it may not be able to shake it. It is probably more complicated than that.

Hi guys,

In my Bristol, there are two pillow blocks installed on the shaft and each have a little grease cup in top with a spring loaded cap. *Does grease go all over the keel under the shaft (I am Awlgripping white the entire engine room)? I found a few extra pillow block bearings in a box; I am wondering if they are good or not. They appear to be just steel with no babbit or bearing material in them. Is this right?

Also....I see Belfast Cruiser's boat appears to be a Bristol? If that is the case, then I'm going to have lots of questions for you!

Kevin, First, a "ball park" alignment is a bad idea for a number of reasons. You either do a proper alignment or leave it alone. If you don't know what you are doing and feel it is necessary, then have a professional do the job. They can then teach you how to do it right the next time. Screwing up the alignment will create some very, very expensive problems. Chuck

Capn Chuck wrote:
Kevin, First, a "ball park" alignment is a bad idea for a number of reasons. You either do a proper alignment or leave it alone. If you don't know what you are doing and feel it is necessary, then have a professional do the job. They can then teach you how to do it right the next time. Screwing up the alignment will create some very, very expensive problems. Chuck

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*To back Chuck on this, I had my marina do an alignment when I did my repower of the old Mainship. I had paid the yard to set the engine in place and line it up, and their diesel contractor (marina cousins) *frigged it up (was off by 3/4 of an inch).

So my marina made it good by getting thier gas engine mechanic (who is outstanding by the way) to correct the alignment. He did it in about 1* hour, and that included disconnecting the intermediate bearing from the bulkhead and moving the engine over by *3/4 of an inch. I went in later and re-mounted the bearing.

So fo an hour or so worth of labor it ain't a bad thing to pay for.

*


-- Edited by jleonard on Tuesday 6th of December 2011 10:15:17 AM