Raw water plumbing to stern exhaust exit

[Mike_W.]

When winterizing I usually disconnect the raw water at the strainer. There is just enough hose length to stuff it into the jug and pull the pink antifreeze through the system until it spits out the exhaust. This past fall it did not spit out the exhaust but instead came flowing out at the prop-shaft. Turns out that my shaft seal is fed raw water, not just vented. I'm inclined to leave it that way after reviewing PSS installation instructions. However, it concerns me that it behaved differently this year, as usually it spits out the exhaust.
Well, it took me until now to finally investigate and I found the raw water is split three ways - to feed the exhaust riser, the PSS, and also all the way to the stern to a nipple on the exhaust outlet, just at the through hull. Why does the raw water feed to the exhaust outlet?

 

[Second Star]

It is likely the anti syphon vent for the water lift muffler, but the arrangement seems odd. My vent exits out the stern about 1 ft above the exhaust so that air can be drawn in once the engine and the pump, stop. With it exiting via the exhaust my fear is that the vent would draw water and defeat the purpose of preventing water flooding the muffler then working back into the engine. But if your exhaust is well above the waterline when not motoring it may be OK.

 

[Kenneth K]

The small hose to the exhaust thru hull should be the vent for the raw-water vented loop. This loop prevents a siphon from forming between the raw water pump output line and the injection elbow--the point where raw water is injected into the hot exhaust hose. This was the typical installation for most Ericsons.

Feeding the PSS with pressurized water is unusual for a sailboat. That is typically a powerboat thing where the PSS is subjected to higher heat. Most sailboats vent the PSS (if at all) to an open-air point as high as possible in the engine compartment or cockpit coaming. Your setup may be ok as long as you realize that any break/leak in that PSS vent line will sink you boat.

As to antifreeze pumping out of outlets other than the exhaust hose, it likely points to your injection elbow being blocked. Fluid from the pump can't make it past the elbow and into the exhaust hose like it's supposed to so it's exiting the other available outlets.