My HTM has hudrulic steering on the outside but it is run off the factory merc steering inside the boat with telaflex from the helm? Why?

That's an add-on kit just as you stated, (assist). They're about half the price of full hyd. They help out the stock type steering pretty well but not like full hyd. to the helm. HTM you're probably not criuising around at road speeds? Depending on what brand it is you can upgrade to full hyd, but you have to change the ram as well or go w/ double.

The ram looks just like any other Hydrulic steering ram I was thinking i could just change the helm and do away with the internal merc steering?

That's what I thought but on the Imco kits the cyl. has a smaller capacity to keep it the same speed as the cable since you don't want the hyd. assist to overpower the cable. As for the other brands I'm not sure, I've only done upfits on Imco's

thanks for the help