Welp got water in the oil. Took a valve cover off and have milkshake all over the rockers and wat not. Is it pretty easy to suck water in through the headers when running water through them while idling? I also have to install the timing cover/ waterpump plate myself. Is it possible to get water in the oil through there? On sunday we acidently had the header valve open when we started it to check the timing and it seemed to kinda have a hard time cranking and ran boggy for a few seconds kinda how a jetski runs when it sucks water in. Now i dont have a valve on the water inlet from the pump. My buddys dad said they never ran one during the 20 years they had the boat and never had a problem.
You should have a valve on the pipe from the jet. If one of your water lines were to break, and your in the middle of the lake, you would have no way of stopping the water from coming in the boat. It's not likely, but possible. I've had to replace some of my water AN fittings because they were so corroded or worn from rubbing the floor of the bilge.
Does that REX valve up front control water to the headers or water to cool the motor?
As for the water in the oil, when I have my inlet valve (ball valve on the pump inlet) open all the way I get a milk shake. I closed my valve a little and haven't had water in the oil since. This isn't the best way to control it. I need to balance the outlet or go with a pressure relief setup. Do a search about controlling temperature, it has been discussed ALOT.
Definetly put the ball and spring back in the tee valve for the headers. You should have either a fine mist or no water at all at idle. If you see water running out of the headers at idle, it's too much. I think REX has restrictors you can put in the water injection lines to get less water to the headers.
BOAT means "get a second job sucker!"

Good luck.