Pressure relief is set to 15psi it dumps through a thru-hull fitting. The combined length of pressure relief valve, ball valve, sea strainer, and flush connector puts the water outlet just behind (and beside) the port side engine mount necessitating a big looping u-turn of some sorts to return to the rear of the logs + I believe it will drain better when I open the drain petcocks this way.
This its just my opinion and you are in no way obligated to listen to me.
I would bump the pressure relief to 20 psi. My reasoning is pretty simple, depending on what size pipe/fittings/hose you have used from the pump, by the time you get through the 10' of hose, the strainer and the tees, your net water pressure would have taken a hit of a few pounds making the block pressure only about 12psi. This is really not quite enough to prevent some stream pockets from forming in the heads causing a potential detonation or flash overheat issue.
There is nothing circulating water in the block when the stat is not calling for cooling...
Also, I recommend feeding the rear of the manifold first. Explanation is simple, coldest water to warmest exhaust, again, counter flow.
Another recommendation I will make is to run the hoses from underneath the motor. Explanation again is what you have already experienced, you have made a perfect inverted trap so that every time you shut the motor off, the sediment will run down into the engine where out can get trapped in the block.
If the hoses are the low spot, the crap settles in the hose where the velocity of the water is much greater than it its in the block. Reduces trapped silt ten fold.
Again, just trying to get you pointed in the right direction.
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