Isoflex vs R&D coupling

[sailingunity]

I'm having a new prop shaft made and the old coupling had to be replaced (loose on shaft). The place that is making the shaft is giving me a choice between R&D and Isoflex.

Seems like two completely different designs. Isoflex appears to be a large chunk of stiff rubber while the R&D is some type of composite plastic. Supposedly the R&D has a fail safe in case of coupling failure it will still maintain some type of connection.

Shaft is 80" long but only about 10" protrudes in the water. I have a traditional stuffing box about 19" behind the engine. Yes that's a long stern tube!

Which coupling would you get?

[FPNC]

They both work. The fail safe is a nice feature as sooner or later anything can fail.
Also, you can easily check the shaft alignment on the R&D models without removing or loosening the coupling. That's the best feature.

[sailingunity]

Originally Posted by FPNC

They both work. The fail safe is a nice feature as sooner or later anything can fail.
Also, you can easily check the shaft alignment on the R&D models without removing or loosening the coupling. That's the best feature.

Sounds like the R&D wins out, thanks for the feedback.