Globe Drivesaver worked as designed

[rslifkin]

I'm thinking that a drivesaver would be most likely to prevent damage with a combination of a very sudden stop of the shaft, a somewhat weak trans and strong enough struts, etc. to not have the shaft rip other components apart.

 

[Steve DAntonio]

In my case, PO installed them and I will keep them. I have everything back together but need to buy a dial indicator to measure TIR. I didn't notice any new vibrations or thumping but with Lehman soft mounts it's hard to tell.

Are you able to bring coupling faces together without DS to check alignment?

 

[Comodave]

Unfortunately my brand of drive savers, I am not sure which they are, are about 1 1/2” thick. They were on the boat when I bought it. The shafts will not come close to reaching in order to do a proper alignment. I looked at the Spurs website and they say their spacers are 1” but I think they can make a thicker one. Hate to think what a special custom made one will cost.

 

[Steve DAntonio]

Unfortunately my brand of drive savers, I am not sure which they are, are about 1 1/2” thick. They were on the boat when I bought it. The shafts will not come close to reaching in order to do a proper alignment. I looked at the Spurs website and they say their spacers are 1” but I think they can make a thicker one. Hate to think what a special custom made one will cost.

If you can move the coupling a hair over half an inch, the standard shim should work.

 

[SoWhat]

Are you able to bring coupling faces together without DS to check alignment?

No. With the spurs on there is only 1/4" of space for shaft movement.
The alignment looks to be dead on but that doesn't necessarily translate into a straight shaft. DS is a polymer that will soak up a lot of misalignment.

Will be at Harbor Freight tomorrow to buy a dial indicator.

 

[Comodave]

If you can move the coupling a hair over half an inch, the standard shim should work.

No, I can’t. The shafts are not long enough.

 

[Steve DAntonio]

No. With the spurs on there is only 1/4" of space for shaft movement.
The alignment looks to be dead on but that doesn't necessarily translate into a straight shaft. DS is a polymer that will soak up a lot of misalignment.

Will be at Harbor Freight tomorrow to buy a dial indicator.

The DS actually soaks up very little, if any, misalignment, at one time they claimed it did but stopped because I suspect they were fracturing from just that, absorbing misalignment. The website says it "DRIVESAVER® provides a flexible, non-metallic barrier between your transmission and propeller shaft. This barrier reduces drive-train vibration, resulting in reduced noise and more efficient operation [I'd love to see the scientific testing that proves this]. Absorbs shock, prevents electrolysis, acts like a circuit breaker, installs easily" No mention of alignment.


Just FYI... The dial indicator will show a bend in the shaft, at that location, or a shaft that is not centered in the coupling. It will not indicate misalignment.

You could use two Spurs shims...

 

[jleonard]

From the Borg Warner manual regarding alignment and flexible couplers.

 

[catalinajack]

No. With the spurs on there is only 1/4" of space for shaft movement.
The alignment looks to be dead on but that doesn't necessarily translate into a straight shaft. DS is a polymer that will soak up a lot of misalignment.

Will be at Harbor Freight tomorrow to buy a dial indicator.

Two options. One: with boat in the water, have a diver remove the spurs, slide the shaft forward, do the alignment, slide the shaft back, install Drivesaver, diver puts spurs back on. Two: have the Spurs folks make a spacer for you if they do not have one in stock. You just need to tell them the part number of your Drivesaver (I think you said it was a #504) and the diameter of your shaft. If they don't have one in stock they will machine one for you in short order. When I replaced my two Drivesavers with their spacer they only had one in stock. They did not charge extra for having to make a second one.

I'll say this again, if it were I, I would have the shaft removed and checked for straightness. If bent, have it straightened or replaced. If that shaft is bent, you will forever have some level of binding and unnecessary and harmful friction going on. The fact that you had to use a pipe wrench to turn the shaft after removing the rope is telling. Consider returning that new Drivesaver and spending the money on a spacer instead.

 

[angus99]

I know a lot of boats wih big block gas or 300+hp Diesels that have choked motors without doing damage.


Especially from just lines wrapping.


Not saying it won't happen...just that it doesn't automatically mean it will cause damage.

We ran over a very large mooring ball pennant at idle speed in the dark on our first run up the coast five years ago. It stalled the stbd 135 Lehman and I was bracing for the worst. We hauled shortly afterward and there was no damage anywhere.

 

[Steve DAntonio]

From the Borg Warner manual regarding alignment and flexible couplers.

That's an excellent excerpt from BW.

I'll reassert, the DS is not a flexible coupling; there are manufacturers of true flexible couplings, https://www.pyiinc.com/flexible-shaft-couplings.html I'm not advocating for these, I believe they are unnecessary in all but a very few cases and represent a weak link in the drive train, and they promote acceptance of poor alignment. I could see using one if a hull really were that flexible, perhaps timber, with a longish shaft, perhaps...