The WP line is very small and pretty hard/rigid. Id guess something like 1/8″. The material is a nylon-type plastic that is not flexible. Its pretty rugged as you dont want that to break between the motor and WP gauge as you will pump a significant amount of water into the boat or dash or whatever. Ive installed a few on Mercs. Typically the kit uses compression fittings if you know what those are. Tiny brass fittings that slip over the line, then the compression fitting crushes that to lock the line into the fitting. You have to install a T fitting in a water line, usually you cut the one between the two cylinder banks, and put the T there. I have seen some with the T already installed and plugged, dont know whether the factory, the rigger, or what does that. I think the last water pressure gauge someone brought by to get some installation help came in a box with tubing included, but I might well be mistaken. Certainly your dealer would have em or can get em quickly. 15 psi sounds fine. I personally shoot for a minimum of 12 psi and have never burned a power head up. The higher you jack the motor, the easier it is to drop the water pressure too low. Particularly in long sweeping turns which can expose the water intakes on the sides to air. If you have the low water pickup version of the opti, you will be fine. If not, just watch the WP gauge in the turns to learn where/when/if the pressure drops off. My current boat has to be trimmed down a bit or pressure will drop all the way to zero. Wont hurt for a couple of seconds, but in a long sweeping turn, I could probably smoke the thing If I tried.2008 Pantera Classic2014 Mercury Pro XS 200
