I have just finished putting together my 383 and had my first start yesterday on a stand. It runs nicely, no issues, but I didn't run it long enough to warm up. Just checked for noises, oil pressure and smoothness. I didn't have it balanced by my guy, so the smoothness was important to verify.
I am wondering if any of you have had any problems with cooling water flow out the riser tails, the EMI risers only let out a little water unlike the flood the OE Mercruiser exhausts give. I'd guess the EMI's only flow a few gallons a minute on the hose. Maybe they might increase when the circ pump is turning though.
Am I just being too anal?
I imagine Eddie Marine knows what they are doing and I'm overthinking this. I suppose I could drill and cut for more water flow if needed.
Perhaps the EMI's are just allowing the amount of water that will cool things and not be as prone to revert. My cam is kind of aggressive for a marine small block. It's not a maxed out dry tail only deal. But because I went with increased compression, I needed enough cam to support the engine. And enough cam turned out to need good exhaust.
So what to do? Run it & monitor I suppose?
Perhaps I can plumb in a cooling water dump system if needed.

I would try it as is before modifying anything. Running on the lake will give more pressure and volume than on the hose. Just monitor Temps. My 383 in the Challenger, I relied solely on the water pump in the Alpha SS, no circ pump. Never had any cooling related issues. Always used a new water impeller every season.

Thanks ! LOL.

How's the old girl doing? Was always a bullet proof drive for me. Ran the crap out of it. Oil always looked great and magnet had fine mush on drain plug every oil change.