Shaft alignment

[jibes138]

How come boat shafts aren't connected by a universal joint like in a car? Seems like the automotive world figured this out a long time ago. Would make all this work trying to get perfect alignment much simpler. Even with good alignment motors are rocking, vibrating, pitching, shifting, etc. as the boat is pounding into waves and the hull is distorting from forces from the wind. Wouldn't a universal joint relieve the lateral forces on the cutlass and stuffing box? What am I missing?

 

[dlochner]

Interesting question. There are these devices, but there are caveats out there about using them to reduce vibration and the engine still needs to be aligned properly.
Globe Marine || DRIVESAVERS
R&D Marine Flexible Shaft Coupling Vs. Globe Rubber Drivesaver - Seattle WA

 

[Stu Jackson]

Dave, did you forget you asked this same question some time ago?

https://forums.sailboatowners.com/index.php?threads/shaft-alignment.109575/page-2

 

[jssailem]

Dave, did you forget you asked this same question some time ago?

I'm guessing here. Perhaps he did not like the answer he got then and is hoping that a new answer will be submitted that better fits with his interest.
Anyone have a new suggestion?

 

[jibes138]

Stu,
I can hardly remember my own name never mind 8 years ago :>)

The info on U-joints not made to take the thrust loads is interesting. In a car the U-joint is at the coupling to the rear wheel differential. So using the same logic in a boat you would put the U joint right in front of the cutlass bearing. If the thrust was transferred through the strut instead of the engine mounts you could probably make it work. Fouling of the U-joint with marine growth would be a real problem. It would have to be sealed, oysters growing in a U-joint sounds like trouble.

 

[All U Get]

For Stu, eight years was like yesterday. While getting mine done I did ask about the drive savers. They do fail according to John (our mechanic) and then you have to mate up the coupling anyway. How many of us DIY sailors using drive savers?

All U Get

 

[Bob J.]

How many of us DIY sailors using drive savers?All U Get

Because I'm installing an electric drive I plan on using one. Has nothing to do with vibration issues, it isolates the electric drive from the prop shaft which is a smart thing to do on an electric boat. If it wasn't for that issue, probably wouldn't install one.

 

[All U Get]

Just did a fuel up and noticed better fuel mileage with the alignment.

All U GET