Flipping Scupper Outlet and Exhaust Outlet.

[Robert1224]

Ahoy,
In the re-power I am doing I am thinking about changing the function of two thru-hulls. In the Nanni 3.21 it states the height of my exhaust outlet should be higher than it currently is. Currently it is a bit over 5 inches above the water on the counter. (Counter being the underside of the hull where it rises to meet the stern)
The drain for the scuppers is under the boarding ladder, centered on the stern and over nine inches above the water. These both are 2 inch fittings and I can think of no reason not to bring the exhaust out the upper which is centered on the stern and the scuppers out of the old exhaust on the counter. The hardware fittings will be swapped as well. Thoughts?
Thanks,
Bob

 

[Dalliance]

Hmmm....something else Hunter changed from one year to the next.

You didn't say, but I'm assuming you have two scuppers in the cockpit connected to a T or Y fitting and then out through the transom 9 inches above the at rest water line. In contrast, my '82 H30 has two cockpit scuppers but the hoses cross to separate through-hulls on opposite sides - port to starboard, starboard to port - on the "counter" (I'd never heard that term before, but it works for me.) at probably about 5" above the water line. It's done this way to prevent water from sloshing up the hoses into the cockpit and it's effective most of the time. If you have two scuppers joined by a T or Y fitting and you connect it to the lower through-hull "on the counter" (I assume to one side or the other of the centerline.) instead of to the higher one centered on the transom, you may find you occasionally get water sloshing up into the cockpit.

FYI, my exhaust exits "on the counter" a bit forward of the scupper through-hull on port side. I've never had a problem with it that I'm aware of.

 

[Ed Schenck]

Curious as to why Nanni wants it higher. I want my exhaust outlet lower, in the water where I can hear it gurgle. My new Yanmar had no such requirement. But you do need either a waterlift muffler or some other way to keep water from backing up into the cylinders. In my case I kept the original big loop in the engine compartment.

 

[Robert1224]

Curious as to why Nanni wants it higher. I want my exhaust outlet lower, in the water where I can hear it gurgle. My new Yanmar had no such requirement. But you do need either a waterlift muffler or some other way to keep water from backing up into the cylinders. In my case I kept the original big loop in the engine compartment.

Ed,
Thank you for your thoughts. That is a great looking, very clean installation. Nicely done!
Regards,
Bob

 

[Ralph Johnstone]

In the Nanni 3.21 it states the height of my exhaust outlet should be higher than it currently is. Currently it is a bit over 5 inches above the water on the counter.

My exhaust outlet is even lower than that ................ about 3" below the waterline.
What keeps the water from entering the engine is the large loop in the exhaust lie just before it exits the hull. It rises about three feet above the waterline.

 

[Bill Roosa]

Scuppers as an engine exhaust outlet are right out. Don't pump exhaust gas into the cockpit. CO is really bad for the crew.
I believe that with a anti-siphon loop you can acheve the height needed and still exit where you want, assuming you have the room to install the anti-siphon loop

 

[Robert1224]

Scuppers as an engine exhaust outlet are right out. Don't pump exhaust gas into the cockpit. CO is really bad for the crew.
I believe that with a anti-siphon loop you can acheve the height needed and still exit where you want, assuming you have the room to install the anti-siphon loop

Bill,
Thanks for the sound advice. I believe I wasn't clear though, I am not considering sharing scuppers or exhaust outlets. I am simply considering switching their locations and keeping them dedicated and separate from each other.
Regards,
Bob

 

[Bill Roosa]

GREAT! I had visions of dead sailors adrift after a nice sail........
The engineering does not care where the exit is. It only cares that outside water CANNOT get in and sink the boat or flood the engine (and then sink the boat). Thinking anti-siphon is the answer here.

 

[sandpiper10471]

I don't recall that instruction from the installation of the Nanni 3 on my H37C. My exhaust exits a very few inches above the waterline forward of the counter. The first two seasons the engine was perfect. Then suddenly it started experiencing serious hydro lock. Solution was an expensive water lock muffler and an anti-siphon loop. I suggest both from the get-go. Both may not be necessary but a lot better than locking the engine and possibly bending connecting rods etc., not to mention the embarrassment, inconvenience and mess of pumping out all the water and sludge at an anchorage and scrounging enough oil and filters from fellow sailors in order to become mobile again.