Aluminium and stainless steel are the worst of enemies.
Put them together in the marine environment and you have all out war.
Whoever decided to make those fittings from alloy should be horse whipped, hung, drawn and quartered and then made to walk the plank.
If you want to be able to steer your own ship long term, you have a job ahead of you which is to completely replace those steering fittings with stainless or better still bronze and while you are at it replace that horrible alloy tiller head with a stainless one.
Just my educated opinion. Your yacht and your pocket and your decision.