Is a pressure regulator needed between dominator jet and engine

[LBPICKLEFORKHYDRO]

and at what pressure should it be at

[Aluminum Squirt]

I'm not very familiar with the dominator but I would say yes. Do a search, this topic has been covered about a 100 times. There are many ways to do it, from regulator to bypass, store bought, pieced together etc. I think around 15-20PSI is what usually works. It just saves a lot of headaches down the road. No water in the oil, no gasket issues, better cooling, better chance of getting a good consistent operating temp out of your set up, etc. I may be way off base and the dominator only produces low pressures, any smart dominator guys out there? Remember these are car motors, cars have radiators, and most radiator caps are designed to release around 7-15 PSI depending on what type of cap. That should be your guiding priciple. There are plenty of motors with good gaskets running at 35 PSI, but my question is why should you have to worry about it, fix it once the right way-Aluminum Squirt

[SmokinLowriderSS]

As far as I know, the Dom gets cooling water the same way the rest do, from the high-pressure side of the impeller.
Depending on your cooling setup, maybe you do, maybe you don't. If your cooling system does nothing to restrict water flow OUT of the boat, then you can restrict the water flow incoming and never get overly high pressure. This is the way my Taylor has run for 28 years. 5/8 lines, log exhaust, and a valve in the inlet line at the pump (threaded to the pump steel line as the pump may generate 300 PSI). I am now running jacketed thru-transom headers and, though it has altered my flow routing somewhat, it has not altered the volume out of the engine.
Folks running INJECTED headers usually install a Banderlog (or similar) valve to stop water going to the headers at idle, also they use less water then jacketed headers do, so the excess must go somewhere. Most of those setups I have seen discussed I believe valve the incoming water, put in the banderlog, and put in an overflow outlet on the transom to pass water at idle and to pass extra water at higher revs.
Some folks with both systems use regulators, some do not. What exactly is your system setup?