My 448 throttle cable was OK until I lubed it, and the slipping got worse after I repowered with a P218 Onan. The throttle creeps back to about 2,800 RPM and stops there. I have a metal block that I put in the throttle lever hole to keep it at WOT. When not in use it hangs on a piece of chain looped around the steering sleeve. Having been a boat and later an aircraft meck I have dealt with lots of cables. I had installed a clamp on my 448 throttle cable to increase friction but the cable outer coil opened up defeating the purpose of the clamp. The clamp is a device intended to squeeze the outer casing to cause an increase in friction, sometimes they work and sometimes they don't.
Two years ago I got involved in a boat project and removed the hydraulic controls and replaced them with push/pull cables. It was a flybridge boat with dual station and twin diesels so there was lots of hydraulic stuff to remove and then snake the cables thru. The cables were large marine type and they were prelubed at manufacture.
Some folks put a kink in the cable to increase friction but I am not in favor of doing that. If any of you folks have done cable replacement on MerCruiser Inboard/Outboard units you know the heartburn that you can get into with kinked cables.
Bob Mac in CT