I'm good with that. I'm not worried about back flooding from the exhaust outlet on the stern. It's height above the waterline - plus the additional climb to the top of the loop- is safe.

But I will have to add a vented loop(as your drawing shows) to the raw water line before the injection elbow. And I will have to raise that elbow to be above the waterline(hopefully to the 12" min.)

I'm in the same boat(pun intended) as this drawing: raw water could eventually flood the engine if the raw water pump was cranked long enough to fill to the manifold. Not something that should ever happen but a higher capacity muffler was my thought. But the size simply won't fit. I'm a little tight; the muffler will be just aft and to port of the engine and transmission(I think). That's the lowest spot available. From there, all up. But the lift distance isn't too severe(as you see in the drawing).