Securing prop & shaft in place

[anpgr]

I'm replacing my prop and shaft - might go into the reasons in a different thread.
Motor is Bukh DV10 - so not a lot of power - about 10hp.
The current setup is:
Shaft - to - coupling: Shaft coupling with 4 bolts that go through grooves on the shaft - so the shaft cannot move at all. It was a pain to remove shaft from this coupling.
Prop to shaft: Bronze nut with grub screw

The supplier making my new prop/shaft recommended a nylock S/S nut with no grub screw - says this is adequate.
Also recommended new coupling with no taper/grooves/grub screw. I.e. shaft is just held by friction using 4 bolts. They claim this is adequate.

What do you think - sounds like I need to tighten these bolts/screws pretty tight - but will this be enough? I am a bit concerned.

 

[TernVI]

I'm sure our shaft has only two bolts clamping the coupling onto it.
To be fair, the 'dripless' seal would stop the shaft leaving the boat.

The prop nut holds the prop onto a taper. It's normally not trivial to remove the prop once you've removed the nut.
If the taper is damaged, that's when props come loose.

 

[Tranona]

Both quite common and perfectly adequate. You could always add a tab lock washer behind the prop nut as extra security.

 

[Boater Sam]

Being old fashioned I still like a stainless steel split pin through a drilling in nut and shaft.
Clamped on couplings are the norm now and are fine.

 

[anpgr]

Thanks for replies - feeling a bit more relaxed now since it's common practice. Might buy a torque wrench to make sure all is tight enough .