They way I have always done it is put a gate valve, like a for a garden hose, at the water inlet from the pump. Then run that to a regular open tee with each end of that tee going to both inlets on the water pump cover. Then one of the exits off of the t-stat cover exits goes to the bassett t-valve and off to the headers. The other exit on the t-stat cover goes into a second gate valve then off to a dump.  I hope that was understandable I normally send a drawing but can't from my phone. You use the first gate valve to slow up the water going into the motor and the second you use to some what control heat and pressure to the headers.

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Plumbing aside, something else i want to remind you is that you MAKE SURE that the first time you start the boat with new freshly chromed headers on is that you make sure they are clean of any grease and finger prints. What ever is on them the first time you heat them up will get stained on them FOREVER. So make sure to wipe them down thouroughly before heating them up the first time.

I have mine set up just like Wog's but you use the first gate valve to adjust engine temp, and the second gate valve (on the dump line) to help regulate when the water starts flowing into the headers.  You don't want water flowing into the headers below 1800-2000rpm. 

More back pressure=lower rpm,   less back pressure=higher rpm.

You're confusing me a bit when you call the line that supplies the water to the headers as a dump line. I thought the dump line was the line that removed excess water from the system? As far as below 1800-200 rpm goes, I don't want any water thru the headers at all?

So as far as the gate valve off the pump, should I be running something like this? I got this image from another forum.

That looks like cas's set up right there. I kinda like the way he has the 2 valves so he can adjust the headers and engine independently.  The way crew chief is describing is like how bassett describes on their websight. My boat was set up like that.....I prefer to shim the bassett valve/spring to adjust what rpm the headers get wet....as opposed to chocking off the dump line. There are a zillion ways to plumb a jet boat. My opinion is no t-stat.......put a pressure gauge on in and ad a regulator IF you need one....I never have. In a nut shell you have 2 dump lines....your main dump....and the line going to the headers is also a dump. The valve up by the seat is just an optional precautionary device.IMO having said that I could have used one a few times this year. I had a piece of sillycone stick my valve open is time out this year. Was at powell idling through castle rock pass when I noticed my headers were wet....looked like the spring rusted in half. Got a new spring....gave her a little stretchy poo and she broke 1st time out. Thank god for vise grips. =)