Check this thread at Boat Freaks.com
Shows dump valve I made.

http://forums.boatfreaks.org/showthread.php?t=9196

Did you ever get this resolved? I would like to hear the fix, since I have a very similar problem.

Funny you guys bought this thread up again. I just fixed the problem this past weekend and couldnt be happier.I ended up using a cross over with a 1" bypass hose.At first I ran the recommended thermostat and my temps were all over the place.Then I drilled holes in the stat and that helped some.Then I removed the stat totaly and I couldnt believe it but my temps stayed at 120 while idling and 130 when wide open for long periods of time.My pressure is reading zero at idle but goes up to a max of 14 to 16 at wot.So I ended up removing the water circulator pump, hoses, and all the extra water dump hoses I added all summer long. So now I have a nice clean looking bilge again.

Anthony

Let me know if you want to sell any of the stuff you removed, like the bypass valves. If you do email me at [email protected].