Hunter Legend 40 exhaust system 1

[clubmech]

Is anyone else familiar with the oddities of a Hunter Legend 40 exhaust system?

It has a lift muffler underneath the engine so you can't replace without lifting engine. Wraps back around the top of engine to an inverted trap then down underfloor, thru centerline berth, in a pan beam up out of beam into a low cabinet, thru stern bulkhead over the diesel fuel tank, then out a below waterline thru hull. A super long and complex 2" hose run defying all standard design guides. But it's worked for 30+ years with too much backpressure the engine runs hot and smokes.

The water is not cold as it first runs thru oil cooler and then coolant exchanger up to an inverted U with air vent which is actually a non-vented brass bolt. Then it necks down into an inverted U mixing elbow from a 3 cylinder engine by necking down from 1" to a 1/2" side port on the mixing elbow (not a good flow pattern to mix with exhaust. I'm wondering if they did that on purpose to restrict waterflow to reduce backpressure??? Say it ain't so and it's just a crappy design. HDI Marine sells full size mixing elbows with a full 1" port on the heel.

So, who can tell me why they designed/installed it this way. The industry pro's I've contacted can't figure out how it works because the 2" hose is so long and has multiple traps for two high points as well as sagging hose.

I need to replace as cooked the muffler, but looking to simplify and reduce backpressure. If you have appreciate the feedback on how and if it worked well. Thanks.

 

[Tally Ho]

What engine ?

Do you have any photos of the exhaust path?

Could be that some previous owner did some creative plumbing….but hard to tell without some photos and without knowing what engine you have.

Greg

 

[clubmech]

It is original from Hunter. Mack Sys. It is a Yanmar 4JHE which was the standard offering. Mack Boring may have assisted Hunter.
Wondering what other Legend 40 owners have experienced and done.

 

[Scott NIelsen]

What year is your Hunter Legend 40? I have a 1996 37.5 with a 3JHE. I have not had any exhaust or backpressure issues on this boat, my 4th Hunter over 40 years of sailing. The only issues I ever had was with the mixing elbow. They tend to get clogged and eaten away on the inside. I replaced the mixing elbow and all exhaust issues went away. I keep a spare elbow in my spares. I found someone a few years ago that had a whole box of stainless steel ones for a very reasonable price and ordered two. I have a ready spare and the screw piece that mounts on the exhaust manifold in my spares. I expect to never need them as they are stainless and don't rust out like the old cast iron ones. I think I found them on Ebay all those years ago. Ebay is often an less expensive source for Yanmar parts than the Dealers.

 

[marcham]

Water lock muffler ??

I remember seeing that setup, with the 2 in exhaust hose going up the front of the engine and scratching my head.... not the easiest engine install to work on....

I would assume that some previous owner could not get the correct mixing elbow or mixing elbow barb? If you remove the hose barb from the elbow, what size is the hole?

The raw water definitely needs to go though an antisiphon before going to the mixing elbow (they should also be tested every year, they do fail!).

Is there room under the aft birth for a water lock? Something like a Vetus NLPH might fit? If so, you could abandon the exiting waterlock in place.... must be hard to test the mufflers baffles once in a while if you can't remove it....

Keep in mind that the size of the waterlock is directly related to the length and diameter of the exhaust hose, which affects the amount of water it may have to collect.

One design criteria ia that the waterlock must be in the lowest part of the system.... so if they had to go up before going back, then it makes sense to have it below the engine.... I'd have to crawl through your boat to understand your layout better !

Is the exhaust elbow innards clean?