I've used some lighter grease successfully on the steering cable end, I just extended it all the way and gave it a quick coat. Every couple years, clean and repeat. I have a bunch of different lubricants sitting around from years of shop business. I didn't go out and buy anything. Not sure what I would get. Last boat I bought the steering was just like yours, they used white grease on it and it was hard as a rock. On a cold morning it wouldn't turn until the motor bay warmed it up enough to soften up.After cleaning it off I used some light weight food grade grease I had left over from a customer welding job on a canner line years ago (can't believe it has been that long, but over 14 years ago) It has been several years since I put it on and stayed easy turning. I don't think you go wrong as long as you know it gets cleaned off and regreased once in a while.