I have a 22ft Advantage Citation that i am putting a 500hp in. What do i need to do as far as external steering, i plan to put a new steerng cable on also.

Just my opinion but go to a full hydraulic system with dual rams and get rid of the cable.

my last boat was runnig about 560hp, I installed the mayfair single ram add-on unit and it worked great, and they are not a lot of money, I also installed a steering cable.

Go full hydraulic. It is world of a difference in terms of safety and control vs keeping the cable. Single or dual ram I dont think is so important.

I have also seen a cable replacement setup that is hydraulic to the helm in place of the cable. It is made by teleflex. It will not get rid of the slop associated with the tiller arm/gimble ring but it is better than the cable. The best solution is dual ram external hydraulic though.

Rene