Are you sure you are not just low on automatic transmission fluid? After a few years, most systems have leaked/seeped out enough to make the steering to not respond. Over 16 yrs, I added 2 times. There should be a very small screw cap on your console. Not easy to get too or add depending on boat. Add VERY slowly, have throw away towels at the ready. Tiny funnel or flexible tubing off a cheap squeeze bottle works best. When it looks full, replace cap slowly turn wheel full left/right, remove cap add again till just below the top of the fill cap. Depending on how low you are, might take 3 or 4 times. And your good for another few years.
Hope that helps.