Alright heres the deal.  As i can tell I have the auto T fitting hooked up to my injection lines.  But under the driver seat I have lines with a ball valve to adjust how much water goes into the the exhaust, but it is not hooked up.

  I know where then inlet line to this ball valve comes from, but does the outlet go before or after the auto "T" valve?

Does that make sense?

LOL, no, but I'll "wing it", the valve near the seat you speak of should go between the water source and the header control tee, just my .02c and thats how mine was set up (I went backwards on my boat, took the Bassets off and bolted on some logs, still looking for some OT pipes).

Adding the valve is to shut the header water off 100% to ensure no water reversion problems and for WOT speed runs without water, which in turn makes nice blue headers. 

GT

So after looking around behind panels and what not I found out how its routed.  The water injection has a auto T and goes right to headers.

The valve under the seat exits out of a fitting outside the boat on the drivers side, the inlet to the valve runs to the rear and is just cut off, not being used.  Is it possible this was used for adjusting water flow out of the motor to control the temperature?

patha , welcome to So Cal......  Now thats said , im gonna jack your thread for a sec

While using the "ball" valve by the drivers seat to control water to the headers , is the Basset "T" valve still in need of the Ball and Spring or can that be iliminated

I would run them both to be more...well, you know...idiot proof    

GT

Thats what i thought , i just bought a new ball and spring for my "T" and didnt want it to go to waist

Thanks.

Now back to your regularly scheduled program

Always recommend running a positive "shut off" along with the "Bassett/Rewarder" "T" especially with any kind of cam beyond stock (due to potetial "reversion issues )  , the shut off (between the pressure "T" ) also provides a means of limiting the water to the headers , headers will work fine with a very minimum of "mist" . Also water (too much) is a HP robber Heres a pic of Josh's set up (engine mounted manual valve above the temp guage )

In MY personal experience I would eliminate the ball and spring all togeather! If they get the slightest amount of sand or debris in them they will get stuck in the closed position! And can make a new set of headers look old in a matter of minutes!

I use a little inline sand filter delio, picked it up a Ryan Herco for like $20 and works like a champ!   

GT

If you want to check the quality of a T-Bone steak, you could always stick your head up the cows ass, i personally would ask the butcher! (LOLOLOL)

The way the water was ran on your boat originally was in from the jet to a ball valve, then straight to the motor. As it came out of the motor it t'd off. One to the basset t-valve and one ran up to the ball valve under the seat, then over board. particullary stupid I thought since a ball valve is typically used as a shut off and not a regulatory valve.

The theory was to have the ability to pinch down the overboard dump so you can regulate the temp in the motor, but in essance what it does is pound more water out of the headers and build up pressure in the motor increasing the chances of hydro-locking the motor.
so.....
i disconnected the valve under the seat and ran it straight over board.

What i would do if i had to do it over again? From the jet, into a pressure relief valve, then to the  motor, then the headers. I think Tom showed this system to me on this board and I wanted to do that, but sold the boat and didnt get the chance.