Shitty pic but you get the idea
Constructive criticism.
You should not ever have just rigid fittings on the water line from the pump. Especially without some sort of brace. There can be a buttload of vibration in that area and if that nipple breaks off, the boat will surely sink like a stone. There realistically should be a shut off valve and some type of vibration eliminator from the pump to all that hardware. I use hydraulic hose.
Also, like you mentioned, that is not a pressure regulator, but a pressure relief valve. There is still the possibility of over pressurization with that set up. Hope all works out for you.
As an fyi, I think you have had a reversion issue. There should NEVER be steam coming from the headers at anything less than about 1500-1800 rpm.
If you get too much water to the headers, try increasing the dump line size.
GT
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