Shaft Alignment

[MikeHoncho]

I have experiences a bad "rattle" after hitting a log with my '78 Hunter 30 with a Brunton Autoprop. A little bit a vibration but much more noticeable "rattle" sound. It sounds like a hose is vibrating against the hull. I removed my Autoprop and installed my fixed 3 blade that was previously on the boat before the Autoprop with no issues. Put it on and took it for a spin and the sound was much worse and continuous. I could make the sound stop at different RPMS.

I sent the Autoprop in for service and was thinking I had a bent shaft due to the fixed blade having the same issue. Today I dove on it and had my son run it in gear (no prop on) and did not see any noticeable bent symptom while the shaft was spinning but I did notice the shaft was very, very close to the bottom of the hole were it comes out of the hull. I do not doubt it was actually contacting it. I could pull the shaft down while the shaft was spinning and a cloudy material came out as it the shaft was contacting the hull. Inside of the boat with it idling and out of gear I could get the rattle to come at a lot lower volume and could get it to stop by grabbing onto the shaft. I believe the shaft is contacting the hull.

Last year I installed new motor mounts and aligned the engine to the shaft with the shaft being supported by the cutlass bearing/strut and the packing gland. I D/C'ed the shaft today and it stays put and clearances seem ok with the feeler gauge but could be a little better laterally.

For my question (s).......my research seems to result in aligning the engine to the shaft as it sits but it appears the shaft is resting on the hull and I think with a out of balance prop, probably aligning the engine a little lower with the mounts, it is now hitting. Is there another technique I should be using other than described? Is this a packing gland/nut issue? It does drip as it is suppose to and nothing extravagant. It is a total pain to get to were it is located. My thought is to just adjust the motor mounts up a couple turns each to raise the elevation of the engine and, in doing so, the shaft but then how do I align it later being that then the shaft will sit lower when disconnected?

Thanks everybody.....

 

[SycloneDriver]

I remember reading an article years ago that stated a lifting force equal half of the weight of the should be applied to the coupler. In other words connect a pulley above the coupler and hang a weight equal to half the weight of the prop shaft so that the lifting force is applied the coupler. I'm sure someone else can describe it more clearly than I.

 

[RoyS]

Aligning a prop shaft is a very tedious process and it is seldom explained well. As you have noted, it is possible to get seemingly correct feeler gauge values at the motor coupling faces even while the shaft is not correctly aligned with the stern tube. You mentioned that you hit a log. It is possible that the strut has been shifted out of place or deformed in some way. What you should do now is haul the boat and place it on stands. This job can take a few days. With the engine in neutral rotate the prop shaft while looking in the stern tube to detect any visible wobble of the shaft in the tube. That would indicate a bent shaft. While rotating the shaft in neutral feel for resistance that may indicate binding in the cutlass bearing. Compare to neighboring boats. Examine the strut carefully for damage. Check for a tight fastening. Next, do as you said, disconnect the coupling, and raise the motor while aligning the coupling faces. With the coupling aligned, you must have two conditions for a happy future: 1) shaft is centered in the stern tube. 2) No binding in the cutlass bearing. One final alignment check, using your feeler gauges rotate the shaft and recheck to be sure there is no bent shaft or misalignment between the coupler face and the shaft. Some people readjust the alignment after placing the boat in the water but I never have.
If your strut is bent, it can be straightened by a prop shop. Re-bedding the strut after removal while trying to achieve proper alignment is another can of worms. Let's hope you do not have to go there.

 

[MikeHoncho]

I’m confident the strut is fine. I checked with he shaft while it was in the water (scuba), so I’m right where you mentioned with alignment: If I alight the engine to the shaft, it remains not center in the tube but properly aligned with the engine.

 

[MikeHoncho]

I guess I need to align he shaft in the tube first but how do you do it that? If I use the engine to lift it off then that eliminates the ability to align the shaft with the engine.

 

[RoyS]

You have to do as you said and raise the engine. The shaft coupling half seems to stay centered on the transmission half even with the coupling bolts removed as long as the faces are touching each other. There must be a hub in there, but I never really looked. Keep checking for binding in the cutlass as you raise the motor. Assuming the shaft and strut are not deformed or displaced, the only adjustable features are the motor mounts. As I said, a tedious project.

 

[NYSail]

If this started after you hit the log, I would think your problem is not the alignment.... Sure you might be able to compensate for a problem by changing the alignment but is this really fixing it? If it were me I would pull the boat remove the shaft and send it to a prop shop to have them make sure it is true..... they can straighten it if its slightly off. Also, you said you can move the shaft down while it was spinning? The shaft should not be able to be moved at all other than a rotation. The cutlass bearing is there to hold the shaft in place aligned with the coupling / trans. Speaking of, did you check the trans to see if there is any play there?? Sounds like something broke somewhere......

Good Luck!
Greg

 

[dlochner]

I guess I need to align he shaft in the tube first but how do you do it that? If I use the engine to lift it off then that eliminates the ability to align the shaft with the engine.

You do this by suspending the forward end of the shaft so that the shaft is centered in the shaft log and the weight is evenly distributed between the strut and whatever is holding up the forward end of the shaft.

 

[dmax]

When I aligned my prop shaft (1" shaft in 1 1/2" log), I disconnected the coupler and used a couple of 1/4" drill bits to raise and hold the shaft in the center of the log - like in this diagram. I also made a tool with 1/4" rod that allowed me to measure all around the shaft to make sure the there was 1/4" clearance all around. Like everyone says, it's a pain in the butt.

 

[MikeHoncho]

You do this by suspending the forward end of the shaft so that the shaft is centered in the shaft log and the weight is evenly distributed between the strut and whatever is holding up the forward end of the shaft.

Yea I'm seeing where people are either supporting the shaft from above or wedging the packing glad up from the bottom. The boat is in the water so removing the gland isn't the greatest idea to see where "center" is. I'm thinking of just wedging it up a 1/2 or less and then aligning the shaft to it. top/bottom alignment won't be a issue since the shaft is suspended by the engine. side/side is where I can make a alignment difference I think. Does this sound like a reasonable plan until I pull the boat out and center it from looking at the outside?
The motor a is a repower but with the comparable Yanmar just a 2gm20f and the PO installed angle aluminum to reinforce the stringers and added shims to the front mounts. I have about 1/2 of upward thread left on the front mounts so I won't be able to perfectly center the shaft in the log unless I add more shims.

 

[MikeHoncho]

When I aligned my prop shaft (1" shaft in 1 1/2" log), I disconnected the coupler and used a couple of 1/4" drill bits to raise and hold the shaft in the center of the log - like in this diagram. I also made a tool with 1/4" rod that allowed me to measure all around the shaft to make sure the there was 1/4" clearance all around. Like everyone says, it's a pain in the butt.

View attachment 214353

This is a lot easier idea than what I was thinking of milling or 3d printing collars to center it. My problem is that it is in the water so I don't have visual access to the log from the inside.

 

[MikeHoncho]

If this started after you hit the log, I would think your problem is not the alignment.... Sure you might be able to compensate for a problem by changing the alignment but is this really fixing it? If it were me I would pull the boat remove the shaft and send it to a prop shop to have them make sure it is true..... they can straighten it if its slightly off. Also, you said you can move the shaft down while it was spinning? The shaft should not be able to be moved at all other than a rotation. The cutlass bearing is there to hold the shaft in place aligned with the coupling / trans. Speaking of, did you check the trans to see if there is any play there?? Sounds like something broke somewhere......

Good Luck!
Greg

appreciate the input. The log was more of a stick. I don't believe this is a single source issue. I'm thinking the primary issue is the shaft isn't and hasn't been centered in the log since I bought the boat 5 years ago and adding a out of balance prop from hitting the log/stick allowed the contact to be prevalent and continuous under certain RPMS and even more so with the fixed blade.
As I research more, it is apparent to me that what I am hearing (not feeling anything) is shaft tunnel contact. I would on occasion hear it prior to hitting it. After, it was defiantly continuous under certain RPMS. Yesterday I was able to replicate it (although alot fainter) out of gear and the engine idling. I was able to eliminate it by grabbing onto the shaft. I was worried that it was a bent shaft after putting on my fixed blade but now knowing that it is defiantly impacting the tunnel, if not continuously rubbing on it, I can see were the fixed would have made it worse and continuous having a fixed aggressive pitch compared to my Autoprop were the fix was variable. Although I did not mic the shaft while it was spinning underwater It really looked straight.
I'm trying to work this on a step process. I think I'm going to minimize the tunnel issue by raising the assembly and then it it continues then I will be forced to pull the boat, pull the rudder, and pull the shaft and get it all looked at and also change the cutlass bearing and doing a bottom job.
I'm really trying to keep from pulling it as you can imagine.

 

[MikeHoncho]

You have to do as you said and raise the engine. The shaft coupling half seems to stay centered on the transmission half even with the coupling bolts removed as long as the faces are touching each other. There must be a hub in there, but I never really looked. Keep checking for binding in the cutlass as you raise the motor. Assuming the shaft and strut are not deformed or displaced, the only adjustable features are the motor mounts. As I said, a tedious project.

tedious more so when it is in the water. I'm thinking my only option to get it "more centered" by lifting it a bit just to eliminate the tunnel contact then really center it next time its on the hard. We don't pull boats for the winter. I haven't had it out of the water in 5 years.

 

[NYSail]

Some builds don't have the shaft in the shaft log in perfect center but I agree it should not touch and moving it slightly may do the trick as a temporary fix. However, in raising the engine you may now put uneven pressure on the strut / cutlass bearing causing another issue.... it all works together. Thats why when people change the strut it takes a lot of patients and know-how to set it in perfect alignment all the way through the tunnel and to the trans.

Good Luck!
Greg

 

[MikeHoncho]

Some builds don't have the shaft in the shaft log in perfect center but I agree it should not touch and moving it slightly may do the trick as a temporary fix. However, in raising the engine you may now put uneven pressure on the strut / cutlass bearing causing another issue.... it all works together. Thats why when people change the strut it takes a lot of patients and know-how to set it in perfect alignment all the way through the tunnel and to the trans.

Good Luck!
Greg

Thanks Greg. I appreciate you checking on my work flow. It will definitely be a project on my list when I pull the boat

 

[capta]

It is quite possible you have done some damage to your transmission and/or engine mounts as well. These sorts of incidents can cause a cascade of damage.
You stated that you are sure the strut is OK, but how can you tell underwater when we are speaking of hundredths of an inch?
Just a few days back, I saw a picture of a boat sunk in her slip. The caption said the owner straightened his bent shaft by hammering it straight on concrete. I suggest you haul the boat and check things out carefully.
I don't think I've ever seen a fixed position stuffing box. They are all mounted on a flexible hose or tube, so do not let the position of the shaft in the stuffing box be a big factor. The guiding factors are the shaft taper end, strut alignment, the cutlass, and to the center of the engine output shaft. When repairing running gear damage we use a piece of yarn from the rudder (or something from the ground up) where the shaft center would hit, to the center of the engine output shaft, then make all the parts line up with the thread, starting with the strut, then cutlass bearing. Next we would do an alignment. After a few days in the water we would realign the engine after the boat has changed back into her "in water" shape. In a perfect world, if you couldn't hear your engine running, you wouldn't have any vibration or noise from the running gear.

 

[MikeHoncho]

Got down to the boat and the mounts are maxed out so I had to scrub the day and fab up thicker shims. I’ll get back to it next week.

 

[Tally Ho]

When I aligned my prop shaft (1" shaft in 1 1/2" log), I disconnected the coupler and used a couple of 1/4" drill bits to raise and hold the shaft in the center of the log - like in this diagram. I also made a tool with 1/4" rod that allowed me to measure all around the shaft to make sure the there was 1/4" clearance all around. Like everyone says, it's a pain in the butt.

View attachment 214353

I did something very similar…

Removed the coupling, removed the stuffing box so I could see the shaft log, and put some small wood sticks around the shaft to center it.

Greg

 

[MikeHoncho]

I'm claiming SUCCESS. I moved the engine up about 5/16 and symptoms are all gone along with it is shifting without clunking everytime. I think the shaft has been sitting on the tunnel since the day I bought it.
The mounts were maxed out so I fab'ed up 3/4" aluminum shims and with adjusting the existing shims I raised the engine 1/2" and brought it down about a 1/4" to give some adjustability on the mounts. This resulted in about a 5/16 difference between the shaft coupler's existing location and the engine coupler. I took a woodworking bar clamp and raised the shaft coupling to meet up with the coupler then aligned the engine to the shaft down to about 3/1000ths. While doing so I also drilled out three of mount lag screw holes (in the aluminum angle that sits on top of the stringer to accept 1/2' lags since the 3/8ths didn't snug down.
Took it for a spin and no more "Clunking" through RPMs and it appears to be working well. I did have a very minimal vibration that I didn't recall having before but it was minimal and not RPM related.
I did have a tough time getting the packing gland set up proplerly though. It seems to be dripping from between the gland nut and the locking nut and not so much from the shaft. I threaded the gland nut all the way off and found some bronze "glitter" seeping out. I think this was trapped in the tunnel from before.
I motored around for a hour or so working through different RPMS and making hard turns and could not replicate the symptoms I had prior. I'm thinking this will get me by until I need to pull it and then i will probably replace the packing gland, associated hose and possibly the tunnel.

 

[Tally Ho]

Always good when a plan comes together!

Greg