Hunter 31 - Yanmar 2GMF wet exhaust hose question

Jul 7, 2010
30
Hunter 31 Deale
I recently replaced the mixing elbow and wet exhaust hose in our boat.
I replaced the mixing elbow and riser with identical parts and used 2" ID wire reinforced wet exhaust hose.

My concern is that in getting smart on the wet exhaust systems and reading a bunch of sites I'm concerned about the routing of the hose (which I used the identical routing from the original hose).

It appears that the lowerpoint of the mixing elbox "U" is about 5 or 6 inches above the waterline and that sites I have read say 12" is minimum.

Secondly the hose routes from the elbow down to the sole of the boat then has to rise up to above water line level to make the U turn downward into the muffler box. This downward then upward routing allows water to lie in the bottom of the house between the elbow and the muffler box.

Is this something to be concerned about? I have owned the boat 10 years and never had an issue, but now with a little bit of knowledge I have created my own concern.

Thoughts? Comments?
 

SFS

.
Aug 18, 2015
2,066
Currently Boatless Okinawa
I had a 3ym20, and the low point below the mixing elbow was WAY below the waterline. It made a U-turn to travel upward, then another 180 to travel downward into what I assume was a muffler, buried below a fiberglass floor. Another hose took the outflow from there to the exit through the transom, above the waterline. Height difference between the low point and the high point in the first two turns was about 2.5 feet.

I never had a problem, and I never worried about any exhaust water left sitting at the low-point bend (or in the unseen muffler) after shutting down. YMMV.
 
Jul 7, 2010
30
Hunter 31 Deale
Great document, thanks for sharing. Irregardless that it was a BetaMarine document, the laws of physics are manufacturer agnostic. Yes my hose routing violates the principle found on page 26 (or 28), depending on how your pdf reader does pagination. In particular my install violates diagram 18.

My hose routes from the mixing elbow then goes down 7 or 8" to the sole of the boat, passes through a 4" access port aft of the transmission, then bears left (looking aft) through a slightly elevated 4" access port into the equipment bay (batteries, fuel tank, waterbox muffler) on the starboard side of the boat, from there it rises say a foot to get above the inlet to the waterbox muffler than turns downward into the muffler.

I don't have any concerns about the exhaust from the muffler to the transom exit, as it makes a significant loop above waterline than dives down to the exit port in the stern.

I am the third owner of the boat, I do believe my 1986 H31 hose routing is original and not modified by previous owners. Does any H31 owner have any other hose routing that differs?

With the new mixing elbow and cleaning out the heat exchanger flues with my .22 rifle barrel wire cleaning tool, I am really pumping out a lot of water compared to before the maintenance.

As I said either, I have replaced the hose in the exact same location as the old hose and never had a problem. Am I missing something here?

A little knowledge they say is dangerous, am I imaging a problem where the Hunter designers decided there was none?
 
Sep 11, 2015
147
Hunter 31 Marina del Rey
My 1984 H31 hose is routed exactly the same way you describe, never had a problem.