As promised a loooooong time ago I am reporting on the use of Tef-Gel on the prop shaft coupling. After two years my coupling came off 100% rust free and with all the original tolerances intact and not destroyed by a thin layer of rust. It MUST be noted that this was an experiment of my own, and that "lubes" should be avoided on straight or tapered couplings. I am NOT condoning the use of Tef-Gel on couplings and if you choose it do so at your own risk.
Straight couplings MUST always fit with a interference fit. When I ordered this shaft I specifically asked for an extra tight interference fit because I knew I wanted to try Tef-Gel.
Prior to installation I coated the inside of the coupling, the key way, the key and the shaft with a liberal amount of Tef-Gel.. While most of it was wiped away by the very tight tolerances when assembling it the anti-corrosion abilities were unharmed. After removal both the shaft and inside of the coupling have a think feeling, extra tacky layer of protective Tef-Gel.
Mike the manager at my prop shop thought for sure the Tef-Gel would have been totally wiped away and would add noting but it survived. The nice thing about Tef-Gel is that unlike Anti-Seize products that contain graphite or metals it does not add to galvanic corrosion issues.. It also works very, very well as a rust inhibitor..
My coupling came off like it was new with NO penetrating oil and only two bolts with my gear/hub puller.
On my last boat, which was brand new, I ran it for less than three months then hauled to change to a PSS. In just three months of use the coupling was already rusted on!!
WARNING: It should be noted that any sort of lube is advised against in a straight coupling. I know this and still decided the risk was worth it on my own boat. I have seen no odd wear to my key or set screws BUT my coupling was PROFESSIONALLY fitted to a light press fit tolerance that requires some force to mate the two together.
Please use caution when doing this and understand that the fit of these couplings relies on the friction & interference fit so as to not completely "load" the key. Adding lubrication can have potentially bad outcomes and can cause the key and set screws to take more load then they are intended to.
After two plus years it came right off:
Better Lighting Showing NO RUST!!
This photo shows NO Tef-Gel after just three months (note the rust adhered to the shaft that broke off the internal surface of the coupling):