Is this normal? Shaft movement- short video

[Comodave]

I’m still trying to figure out what the issue is? You have a video of a wiggle in your prop shaft that, as I understand, does not manifest into any disturbance in the operation of your boat going through the water at any speed and absolutely not your sweet and economical 9 knot cruising speed.
Where’s the beef? I must be missing something.

Vibration and eventually it will wear out the shaft seal and maybe wear the cutless bearings.

 

[BruceK]

Vibration and eventually it will wear out the shaft seal and maybe wear the cutlass bearings.

Indeed. My previous boat chewing out packing alerted me there was something amiss in the running gear. Sure enough, a bent shaft.

 

[Nick F]

Hi mncruiser - as Steve d´A says, please let us know what happens!
Everyone learns from the final outcome.

Regards,
Nick

 

[JRO]

Vibration and eventually it will wear out the shaft seal and maybe wear the cutless bearings.

Everything behind the coupling including the shaft seal and cutlass bearing are designed to move, wear and absorb unavoidable imperfections in rotation. Even if there was a way to achieve perfect balance and alinement the first barnacle on a prop blade or shaft starts an imbalance. As much as we’d all love perfection there is a point to accept excellent performance and function.

 

[mncruiser]

I’m still trying to figure out what the issue is? You have a video of a wiggle in your prop shaft that, as I understand, does not manifest into any disturbance in the operation of your boat going through the water at any speed and absolutely not your sweet and economical 9 knot cruising speed.

Where’s the beef? I must be missing something.

The initial issue was the dripless shaft seal dripping. There was a spare seal on the shaft that was moved in place, but there are still small leaks while in gear at low rpm (idle) leaks go away at all speeds over idle and no leaks while at rest.

This led to a discussion about potential causes and solutions, enter the video and measuring.

 

[Comodave]

Everything behind the coupling including the shaft seal and cutlass bearing are designed to move, wear and absorb unavoidable imperfections in rotation. Even if there was a way to achieve perfect balance and alinement the first barnacle on a prop blade or shaft starts an imbalance. As much as we’d all love perfection there is a point to accept excellent performance and function.

Not looking for perfection, just to be inside the engineering specs.

 

[JRO]

The initial issue was the dripless shaft seal dripping. There was a spare seal on the shaft that was moved in place, but there are still small leaks while in gear at low rpm (idle) leaks go away at all speeds over idle and no leaks while at rest.
This led to a discussion about potential causes and solutions, enter the video and measuring.

Your dripless is dripping perfectly as designed. You are living a charmed life.

 

[mncruiser]

Old thread, but think I have this all resolved. The TLDR from above was a lot of shaft movement. I ended up running it as-is for the remainder of 2022, and this spring 2023, went forward with a fix, that seems to be good.

After all your advice and working with my mechanics, the decision was made to start with the replacement of the engine mounts. They were original, we replaced with stock Yanmar mounts. An initial alignment was done on the hard, and a final alignment was completed after about 2 weeks in the water.

The thoughts were any work without replacing the old mounts would be questionable because of the state of the mounts. Start with the base (mounts) align...work back and through the system.

So far, the results are satisfactory. When I get a chance I'll hook up my run out gauge and try and post my run out specs.

The tech did mention that "drive savers" are popular for my style of boat. https://www.globecomposite.com/drivesaver

I currently don't feel like I need one, but curious if anyone has used them.

Thanks all for the replies so long ago, took a bit for me to get it all done!

 

[Steve DAntonio]

I'm no fan of Drive Savers. I see them crack and fail because of poor alignment, many seem to believe they can absorb misalignment, for the most part they cannot.

When installed they extend the overhang between the aft end of the strut and the leading edge of the prop hub, potentially beyond the ideal maximum allowable distance of 1.5-2 shaft diameters, and they must be removed to carry out alignment measurements.

I have never heard of a case where a Drive Saver actually saved a drive...

 

[Comodave]

We had them in our last boat when we bought it but removed them for the reasons stated above in Steves post.

 

[Steve DAntonio]

When I have removed Drive Savers, in some cases a shim is needed to maintain the prop to strut clearance, or to accommodate spurs. I have used a precision machined shim available from Spurs for this purpose. I happened to be looking at this on their site today, to include in a report, and noticed that Spurs actually lists "Replacing Drive Savers" as one of the uses for using one of these shims. https://spursmarine.com/spurs-shaft-spacer/

 

[Comodave]

When I have removed Drive Savers, in some cases a shim is needed to maintain the prop to strut clearance, or to accommodate spurs. I have used a precision machined shim available from Spurs for this purpose. I happened to be looking at this on their site today, to include in a report, and noticed that Spurs actually lists "Replacing Drive Savers" as one of the uses for using one of these shims. https://spursmarine.com/spurs-shaft-spacer/

I had Spurs make 2 spacers when I removed the Drive Savers on our last boat. They weren’t cheap but they were nicely done and fit exactly per my specs. Took some vibrations out.

 

[RickyD]

Before I ask some follow up questions about things related to the shaft seal, is this shaft movement normal? https://youtube.com/shorts/f4H9Zn3c9eI?feature=share

Specifically asking if the shaft seems misaligned or is this normal movement? I never paid attention to it before. Thanks

Looks to me like your cutlass bearings may be wearing or some misalignment along the shaft. My buddies boat had a much worse vibration: one strut out of alignment and two worn cutlass bearings.

 

[mncruiser]

Looks to me like your cutlass bearings may be wearing or some misalignment along the shaft. My buddies boat had a much worse vibration: one strut out of alignment and two worn cutlass bearings.

Thanks. This was an older post from last year. I ended up running all last season with no issues.

This spring we replaced the Yanmar engine mounts as they were from 2001, performed an alignment on the hard, and then a final alignment after the boat was in the water for 2 weeks.

All issues seem to be resolved.

Thanks!