what I did was start boat on trailer in water at the ramp, let idle for a while and turn valve down at pump until water temp comes up at idle, I think I am running about 120 - 140 degrees at idle. then I adjust other valve at dump so it starts flowing water out ot headers at about 1500rpm.  After running you can adjust if thats too much water coming out headers while cruising.  Just takes some adjusting to get right but it aint that hard.  I believe if you have a water pressure guage hooked up you  dont want anything over 25psi.

IMHO you can ditch the second dump line valve.

For now, keep it WFO. Start with the gate valve a bit more than half open (meaning if its a six turn valve, open it three turns) and give the motor a rev and note where the headers begin to mist. The boat does not need to be moving, but has to be in the water.

Your headers should begin to steam until over 1500 to 1800 RPM. The dump line should move varying amounts of water depending on engine speed.

What you should see is warmer water temps on the gauge at idle (in the neighborhood of 120-160 degrees and lower temps at a cruise (probably lower than the gauge will read) and warmer again at WFO, not over say 170*F...Organic compounds like calcium carbonate, lime and others solidify at anything over 160*F so that should be your overall goal.

The dumpline should not exceed a 7/16" hole, I think mine is 3/8" and it runs dead on and is always repeatable. I only have a gate valve on the pump and a Bassett tee using a dead man valve on the throttle to ensure water shut off when off throttle...

Good luck and more importantly have fun. 

how much steam should i expect to be looking for

In all honesty it depends on the temperature and the dew point of the air around you at the time.

It should be somewhat like a car overheating....I have had header steam completely engulf the docks on a super cold and humid day...

You'll see...Just look out for water actually running out of the header pipe. That would be bad....

Also, periodically check the weeper holes in the bottom of the headers....They can get plugged with rust/debris real easy...again, bad.

GT

lol that sounds like this is gonna be a bitch to ski behind. ok ill keep an eye on that should water come out of the weep holes a lot or just a little ever here and there

Just enough to make a little mess and really just when you come back down to idle from running above the steam point. (Water condenses once the exhaust begins to cool and there is not enough exhaust pressure to push the water up through the pipes).

what does it mean when there is water coming out of the header pipe at the lake i was 3500 rpm 10-15 psi and water coming out of the pipe

How much water?

If set up properly there should just be some intermittent drips from the bottom of the header pipes.

GT