One U-joint on drive shaft

[Sergy]

Hi everyone my 25 year old boat has a U-joint about 2 “ after coupling it works fine I have no problems I am sure the previous owner must of installed to correct some minor misalignment. Has anyone ever seen this is it a good or bad idea . There is about 5 inches from back of U-Joint to stuffing box. I have considered placing some kind of brace that would retain the shaft in the center if ever the shaft were to break

[jrogers]

Hi Sergy,
Our thirty-something year old Ingrid has a complex drive shaft arrangement that includes two sets of universal joints. They are an older way of compensating for the engine and transmission being about a foot lower than the shaft log. The owner/builder was an engineer and designed this himself. It seems to have worked flawlessly for over thirty years, although his advice was to keep the zerk fittings greased (at every oil change). The modern equivalent is a constant velocity joint which you can purchase from several sources for a drive shaft application.

[Chief Engineer]

I think bracing the u-joint would defeat its purpose.

I have seen some constant velocity joints that come with a mounting brace.

Post a pixture if you can.

[DeepFrz]

A single u joint wont do much for you. You need two u joints at 90 deg. in order to approximate a cv joint. CV joints are preferred.

jrogers, your u joints must be pretty beefy to have stood up so well.

[Sergy]

Thanks guys the brace was not to touch the drive shaft a round opening in a board if the shaft ever broke the u-joint would continue to drive the broken haft which would fling outward and could hit the hull sinking the ship.
I was concerned about the only one U-Joint and I called experts on u-Joints and they confirmed if you have a big misalignment you would need 2 joints but in my case we might be talking 10 to 20 thousand so the single joint would handle. I will ck to see if I have pic. Thanks again

[James S]

I the ones the Chief Engineer is talking about have a brace to counter the trust of the prop. and act as a thrust bearing.
This has the added benefit of adding life to your motor mounts.
I looked at these CVJs recently on my re-power but the ones that fit my shaft size (1-5/8") where incredibly long...like 16in or so.
With out it, the shaft would be subject to lateral forces and movement.