The way I believe it works is the shuttle valve relies on feedback from the tiller arm to direct the fluid from the left to right cylinder. If you turn the wheel in one direction it moves shuttle valve in a direction that sends fluid to actuate external ram(s) to move the outdrive. When the tiller arm moves it returns shuttle valve back to a neutral position.(even fluid flow to each ram). I could not get my half system to work until I hooked the tiller arm back up to provide feedback to the shuttle valve. Without it outdrive would drive in one direction and stay there.

youtube video. installation of mayfair add on setup. from 7 minutes to about 9 min 30 sec. he is disassembling oem steering and replacing with the manifold that send fluid out to the external rams. and you see the piston that used to run the oem system and how it is taken out of the loop. another video. a quickie shows how the brazil valve makes the steering cyl actuate. what he is pulling on is where the steering cable attaches. 3rd little quickie shows how the steering cable actuates the valve and how the tiller end provides feedback even as it is being driven by the piston. what this also shows is the fair bit of valve movement when engine not running which is the 4 inches of steering wheel movement.

So upon further inspection I noticed my add-on system doesn't have the normal valve that diverts the hydraulic fluid from the piston and reservoir to the lines for the external pistons. From what I noticed in the instructions for normal add-on systems, you remove the reservoir/cylinder and plunger from the actuator, then you put on a special valve that slides over the plunger shaft to connect the hoses to for the external pistons. On my 29 outlaw the reservoir/cylinder on the power steering actuator seems to have two fittings on it, one for each hose to the external steering. My questions - Has anyone seen this type of setup? 2nd, my steering is leaking a lot of fluid inside the bilge and (although I have not had a chance to verify 100%, engines were to hot to crawl over and inspect too long) I believe it is leaking from the actuator. Can I order a new actuator and just replace the new reservoir/cylinder with the one on my existing actuator?

Just noticed that this is unique to Latham's add-on system. They modify the mercruiser controller valve. I will call to make sure that I can do what I want.

Edit

so you have this old style actuator? Mercruiser 1990 Alpha 1 Power Steering Actuator | eBay that is supposed to be 94 and older. called a Saginaw valve. the later (brazil) type has to have that manifold to provice the output of fluid to the ext rams. the Saginaw type uses the existing fittings coming out of the valve and caps off the other 2 ends going to the cylinder with hose mainly cuz open cut ends look stupid, not because they need to be closed off. the fitting could be loose where it attaches to the valve, the valve itself could be leaking, or any of the hoses could be the issue. sounds like it is on the low pressure side or it would be spraying a pink fog when running...

I have the brazil valve. Latham machines the outside of the reservoir to put flats on it and taps it. This is the reservoir where the piston slides inside. The hoses for the external rams are attached there. The fluid seems to be around the end of the cable and where it attaches to the tiller arm. It's really hard to tell where it's coming from. But I'm pretty sure it's leaking out of the valve itself. Very hard to see back there. I didn't see anything spraying when it was running. The fittings all seem snug and dry.

sounds like the valve itself. they are cheap and easy to find. you could put your reservoir on the new valve, get the adapter from mayfair, or even use an old style valve and hook hoses up directly to it. so it is this; Latham Marine I think mayfair's setup makes more sense...

I'm resurrecting this thread. I still have a lot of play in my steering. There is like 3 or 4 inches of back and forth on the steering before I see the cable put pressure on the tiller arm pin. So the play is in the steering rotary and/or cable. The rotary and cable are 20 years old. Would a new rotary and cable help my situation or will this play still exist with the new parts? Are there any adjustments? The cable nut at the p/s actuator is tight and the actuator is new. Does anyone know the brand of the steering rotary and cable baja uses?