Driveshaft / stuffing box

[Randomwake]

I’ve got a single engine 120 FL, once the RPM gets over 1700 the shaft kinda starts to wobble and gets a bit of a rotational clunk. I don’t typically run it over 1700 but just wondering if I should doing something while it’s out of the water.

I also can’t seem to get the correct tension on the stuffing box packing, I tighten it until it’s barely dripping ( which I’m told it needs some fluid for cooling and lubrication) but after a while its right back to pretty good flow 2/3 drips a second.

Thanks for the help!

 

[SteveK]

If it were my boat I would determine what is causing it and not keep using it.
Forget the stuffing box for now at least.
Secure boat to dock and run engine in gear at idle. Observe and listen at the transmission and watch shaft to see any wobble.

Your boat is in the water, next I would separate the driveshaft from the transmission by about 1/2", mark the flanges to be able to reattach in the same spot.
Start engine and put into gear at idle. Observe the rotation, is it wobbling, any noise? If no, not trans, stop engine. Next rotate shaft 1/4 turn at a time and see if it is still in line with trans flange. If not then shaft may be bent. If no visible misalignment, then it may be prop damage.
I would do these steps myself to save $.

 

[Comodave]

Yes, if you have wobble in the shaft you need to fix it. Probably the reason the stuffing box goes back to leaking is the shaft is bent or out of alignment so the stuffing gets worn and starts leaking again. Have you done an engine alignment? If not that is the easiest thing so I would start there. Check the coupling and make sure it is square to the shaft. Then maybe put a dial gauge and see what run out is in the shaft if any. That will be the more difficult to troubleshoot. It could be struts out of alignment.

 

[Choices]

Motor mounts. Change them, wait at least a week for them to settle, then align motor.

You can see it done on my blog, grandbankschoices.

Single best mod to my boat, engine was dramatically quieter, zero vibration in boat.

Once you fix that work your way back tightening everything.

 

[Pete Meisinger]

Also you need to check the rubber bearings along the shaft and struts.

pete

 

[RickyD]

I’ve got a single engine 120 FL, once the RPM gets over 1700 the shaft kinda starts to wobble and gets a bit of a rotational clunk. I don’t typically run it over 1700 but just wondering if I should doing something while it’s out of the water.

I also can’t seem to get the correct tension on the stuffing box packing, I tighten it until it’s barely dripping ( which I’m told it needs some fluid for cooling and lubrication) but after a while its right back to pretty good flow 2/3 drips a second.

Thanks for the help!

My buddy's new to him 1989 boat did about the same thing. Anything over 1400 rpms was scary. The boat yard found that this 55 foot boat with two struts each side had the middle strut 3/4" off center, the cutlass bearings destroyed, and the engine flange very loose but the shaft was straight I don't know how this can happen. If you saw the middle strut you'd say there was no way that thing could be bent. Maybe the aft strut could have been bent but that was also hard to believe. But, they moved the strut, replaced the four cutlass bearings, tightened the flange and we ran smoothly on the way home hitting 2700 rpms max.

 

[Comodave]

Driveshaft problems are tough to find. It may take several haul outs to narrow down the problem. Do the simple easy stuff first. But bear in mind that if you leave it it will only get worse as it wears things out.

 

[catalinajack]

Motor mounts. Change them, wait at least a week for them to settle, then align motor.

You can see it done on my blog, grandbankschoices.

Single best mod to my boat, engine was dramatically quieter, zero vibration in boat.

Once you fix that work your way back tightening everything.

Of course, if the motor mounts are good, that's a lot of work and expense for nothing. I had some vibration. Found shafts to be not straight. Also got rid of the DriveSavers. Engines realigned. Vibration gone without changing motor mounts.

 

[SteveK]

Of course, if the motor mounts are good, that's a lot of work and expense for nothing. I had some vibration. Found shafts to be not straight. Also got rid of the DriveSavers. Engines realigned. Vibration gone without changing motor mounts.

Why did you get rid of the DriveSavers, are you saying they contributed to the wobble? I have them in the Grand Banks and plan to install in the Bayliner.

 

[mvweebles]

OP - the wobble needs to be diagnosed and repaired. It will not heal itself.

You should be able to rotate the shaft fairly easily by hand. It doesn't take much to prevent this. It's a decent initial diagnostic test and is simple.

As Comodave suggested, checking the shaft runout is a good diagnostic test. Many of these tools are magnetic base, so may need to fasten a piece of steel to a stringer to use the tool. Not sure what the make runout should be, probably a few thousands of an inch.

https://www.amazon.com/Clockwise-To...sprefix=runout+dial+indicator,aps,162&sr=8-3#

Next step would be an accurate engine alignment. Also check the motor moubts by trying to rock the engine with a long pry bar. For most installs with semi-rigid mounts, it shouldn't move much at all. After that, you will need to haul the boat. Measure shaft runout mid-run; check for any sign of damage (have you wrapped a line or touched bottom? Anything chuncks out of prop missing?). But either the shaff is bent, or the cutless bearing(s) are worn, a strut is bent, or something is broken such as prop.

Good luck. Please update with what you find. Helps us all learn a bit.

Peter

 

[Comodave]

Why did you get rid of the DriveSavers, are you saying they contributed to the wobble? I have them in the Grand Banks and plan to install in the Bayliner.

I had them in our last boat when we bought the boat. We had vibrations so I had spacers made to take up the length of the drivesavers. Then we could do a proper engine alignment. Vibrations were gone.

 

[Choices]

I would agree aligning a engine with drive savers is tough if they are not new. If new not much of a problem.

I can pull my shaft up and mount hub to hub, without that you really need a good tight metal spacer.

 

[Comodave]

I had some custom spacers made for our last boat by Spurs. They were excellent but fairly pricey. The shafts couldn’t be pulled forward in that boat.

 

[Alisske]

Someone mentioned briefly, but in addition to the other comments, i would include thee cutlass bearing.

Gotta be fixed though. I redid all of that in my lehman FL 120. Wasn't that bad out of the water. Cutlass bearing sort of sucked, lol.

 

[C lectric]

The odds are good that the engine/shaft connections simply need an alignement.

There are other causes of vibration such as you describe but I would check the alignement first and see how that goes.

Also get the prop checked for ANY damage. A wonky blade can cause this.

Do the simpler stuff first.
Yes, there are lots of other potential problems but those two are one of the most common.

 

[Northern Spy]

It sounds as if you have a resonance frequency issue which might be aggravated or caused by worn bearing surfaces when the shaft rotation approaches critical speed. Does it have a steady bearing? If so check it. If not, it is likely a worn cutlass bearing.

Do a Google search and read a few articles about shaft whip or shaft whirling.

However, if it a 1x rotational thump, it is likely misalignment. Check your engine mounts.

 

[catalinajack]

Why did you get rid of the DriveSavers, are you saying they contributed to the wobble? I have them in the Grand Banks and plan to install in the Bayliner.

Why? Twice, once on each side, they fractured under load (without having hit anything) leaving me with propulsion on just one side. No, I am not saying they contribute to wobble. What I diid say is that it is near impossible, save blind luck, to get engines aligned within spec (.003-.004) with the DriveSavers installed in the driveline. Bad alignment equals vibration. If you align your engines with DriveSavers installed and you still have a vibration, you cannot know whether or not your new alignment is the culprit. In any case, DriveSavers are expensive and of dubious value. Steve D'Antonio is not a fan. Do a search here and you will find the thread that discusses the pros/cons.

 

[Alisske]

I have aligned FL120s a few times. The low RPM/HP make alignment tolerances really forgiving.

When the boats out of the water, go and shake the propeller back and forth/up and down. If there. Is play, you'll need a cutlass bearing. But take note, if you have bad alignment due to other issues such as alignment/mad mounts/warped shaft then that will eat up a cutlass bearing quick. Im fairly sure you'll need a cutlass bearing in any case. Also, shake it front to back. If there is play, something could have worked itself loose

I would detach the shaft and pull pack and do alignment. Its actually pretty easy on the FL 120. I was terrified of doing it (replaced all my running gear, motor mounts and serviced tranny prior to a long open ocean trip) bit was surprised how easy it was.

That said, my shaft had a very slight warp to it, but it drove it 10 years with no ill consequence. (No clunking). The reason i mention, is that there was a small ring of electrolysis corrosion where the packing was and you would never see it if it wasn't pulled.

Just start with the alignment and cutlass bearing check and work your way through all the gear. It will all work out. I could even be a bad tranny bearing, loose coupler bolts, or imbalanced prop.

Just got start looking. In any case, Good luck. Im sure it will be a straight forward fix