On a add on steering kit do you still leave the tiller arm hooked up with the external ram?

I have not done this personally but from what I have read and seen, YES. With the FULL kit you would replace the helm and cable system.

When I did mine I kept it hooked up. But you have to cut the hydraulic lines from the cylinder to the valve so the cylinder can move. What I did was plug one line and put a valve on the other line so I could "dampen" the steering with an adjustment of a thumbscrew. I can't really say it helped anything. I believe the recommend practice is to cut the lines then crimp them closed, just not airtight.

The other reason to leave the tiller hooked up is if you loose power steering pressure, you can still steer, albiet hard.

BT

I've done it both ways in boats and I recommend that you go full hydraulic if you can swing it. The hydraulic assist does give you safety but not near the precise feel. As far as work goes installing the helm is not that difficult. Eric

Yup, the hydraulic helm makes all the difference.

I won't cost that much more.

I ran add on for 3 yrs and can say I didn't notice any marked improvement in control over stock with the twin engine setup. It was clearly safer and that is why I did it. But now I am north of 90 and the sloppy, hard steering ain't cutting it. I have the helm, valve and hoses sitting on my desk ready to go in. I am really looking forward to having the full vs just add on. My cost to convert to the full should be right around 1800. I got the tilt helm as well which added quite a bit to the cost. I drove my buddies similar scarab last summer with full hydraulic. His felt like driving a cadillac vs my old lumber wagon feel.