I had a 2006 Shelby 22 classic with a 496HO ran 77-78 without a problem and had the stock steering the boat came with. Drove and handled awesome and wouldn't have changed anything about the steering..

Joe

As I understand, an "add on" system taps off the existing Merc power steering. The external piston or pistons are driven in series with the internal piston; the internal piston and connection to the tiller is not removed from the equation.
My intent is to add the external piston as a safety measure on my 20year old stock cable and Merc system. I'm not expecting to notice much more than a little less torque at the wheel. I fully understand that the "add on" system does not get rid of the play at the cable helm.
As for a full hydraulic to the helm, I agree that on a stock powered boat, that 5K is probably not worth it on a boat that does not have handling issues...

WOW.... Do I feel stupid??? was talking to a friend of mine about my steering torque and he asked if I had checked the power steering fluid? No because it could'nt possibly be that! Bingo, reservoir was bone dry. I filled it up and turned the wheel several times added a bit more fluid then took it for a spin and no problem with steering. I needed to find out why it was empty and the hose clamp on the line going into the reservoir was loose and I think that was the culprit.
Too late to do any more testing this season so time will tell? I think I just saved myself several thousand bucks!