The simple answer is that all the water that flows through the raw water system does go out the exhaust elbow. But like so many things "boatish" the simple answer might not always be 100% correct...
On our Amel there is one other route for a small percentage of the water to take, and that is out the syphon break. According to people who should know, the syphon break was a modification that Amel introduced into the production run close to the time ours was built. So in your case, maybe, maybe not...
In any event... a significant restriction of water flow at the exhaust elbow would reduce total water flow through the system. The additional back pressure would also probably reduce the lifespan of your impeller.
Royal Island Harbor, Bahamas.
---In amelyachtowners@..., <sailw32@...> wrote :
Mark, I have always insured that my impeller was in good shape and keep my heat exchanger clean. Excuse my ignorance , but does all the raw water pass through that channel ,I suppose it does . This was the first time I ever had the elbow off. It appears that I have stumbled onto the cause of a puzzling problem I have had for some time. When my rpms went up so did my temperature . Maybe having to take off and rebuild my turbo was a good thing. Cautionary note, I sucked up a paper towel left in the engine room into the air intake for the turbo. I am now putting a screen across the inlet to prevent anything from being suck in.