This subject may have been dealt with previously, but my 'searching' skills are poor, so forgive me if it's a repeat.
My throttle cables are very difficult, and one is not responding well at all; advice from the sages at my marina is to replace them, but I tend to think that they have not been maintained during the past few years, and a search on t'Internet popped these devices up: The last one is labelled a 'Hydraulic Cable Oiler', and appears to be a more heavy-duty item than the others.

Are these of any use on a boat such as a Carver 2827, for the various control cables? They seem to be made more for the motorcycle user, whose cables are very much shorter than those from my bridge down to the engines. I don't want to remove the cables either, other than to release from the control points - is that feasible? Grateful for any advice.