Years back, you could count on the black colored Vulastik L style couplings to fail within the first 1000-2000 hours. They all seemed to and the color of the engine did not matter (on MANS, CATS, Cummins, etc.) and this is when Vulkan developed the Silicone elastomer L “yellowish color ” couplings to help mitigate the problem.
Did it?? No, as I’ve seen them go too……………………………………………..As for Centa, the “Dual-Flex” couplings, they seem to last about 3000-6000 hours behind a 8.3 liter Cummins…….The inserts start “chunking” and spitting pieces out the holes in the bell housing adapter. If you wait too long however, the whole coupling falls apart.
Most companies seem to feel that a few thousand hours is acceptable… Tell that to a single engine boat operator. As for me, I go with the flow and, if I can, I use RBD type coupling where possible as they never fail but don’t offer the controlled “wind-up” that may or may not be needed.
“Sure-Drive” out of Canada offers a lifetime coupling based upon the proven RBD design, has just enough controlled “wind-up”, but is very limited in the selection of coupling it can replace. It is, hands down, the very BEST replacement for the VULKAN or “VL style couplings”. If you currently have a ZF 301C, 301 PL, 301A or ZF/IRM 301VLD or ZF302IV series marine transmission then the Suredrive is a true “Plug & Play” never think about it again replacement.