Your marina would not touch it because they probably have no clue about it.
I currently run both styles in my boats. My older boats (like yours) run cable. I run it up to and including my 1960 Glaspar G3 with a 1960 Evinrude 75hp V4. Plenty reliable enough for twin set-ups as well.
These cable systems when set up properly and the pulleys are nice and free are super nice steering systems with zero slack and very easy to turn.
As far as reliability? these systems are still current systems in a lot of single engine APBA racing. Pretty much bulletproof with occasional maintenance. About the time the clear covering over the cables makes it time for replacement cables is when I go in and check the pulleys, etc.
The shrouded pulleys eliminate the possibility of jumping by the way. Anyone who has done these systems should know that.
It's Your money!!
Oh, the marina knew about the systems. One of them raced vintage boats, and he did the inspections. But guys who race their boats must have them inspected regularly, and they tend to be knowledgeable take good care of their stuff, like you do, no doubt. But regular people use their boats when they can, and typically only check or fix stuff if it acts up.
That being said, would I recommend cable & pulley steering to a regular boater? NO WAY, for the safety reasons already stated.
RichG99 stated above how he had a near miss during an avoidance maneuver. To bring the thought home, imagine if that were someone in YOUR family, perhaps with small kids that YOU love, and they didn't have time to get pulled to safety. If YOU were the one who recommended the old pulley and cable system, and that happened, it would be a heavy burden on you for the rest of your life. Can you imagine the regret you would feel? It would be almost unimaginable.
Of course, ANY steering system can fail, but the cables typically give you a lot more warning before they do.
Not trying to get too heavy or bust your chops too much, but human health and life are irreplaceable. I've learned to be VERY careful of what I recommend to others. As the saying goes, better safe than sorry. Sorry is not enough sometimes.