Wet Exhaust - Is This Mixing Elbow Right?

[model 10]

But there is no flow if there is no exhaust. They both stop at the same time.

[kuljah]

Try looking at American Diesel Corporation www.americandieselcorp.com

Bob, the owner, started the company when he left Lehman. They have regular parts for Ford Lehman engines, including the exhaust mixers and risers.

Btw, I have no affiliation with the company. I just know of their reputation.

[Sailmonkey]

Originally Posted by Guy

But there is no flow if there is no exhaust. They both stop at the same time.

The fuel is shut off, the engine continues to turn and pump water for a second or so. During this time "air" is still exiting the engine forcing water out the exhaust. However once all motion ceases all water that was left either in the heat exchanger, or on the downhill side of the vented loop if installed high will drain into the mixer. This is the part that is the problem. None of this motion stops instantly.

[Liam Wald]

This is the new style mixing elbow for Yanmar.
Looks kind of like the one you are asking about.
I have this elbow on my 3gm30f with 1100 hours and no problems.

[Sailmonkey]

Originally Posted by Liam Wald

This is the new style mixing elbow for Yanmar.
Looks kind of like the one you are asking about.
I have this elbow on my 3gm30f with 1100 hours and no problems.

I'll bet if you look inside of it there's a concentric pipe to direct the seawater further down the bend before mixing with the exhaust.+

edit:

behold, I found the original picture on Ebay.....right next to it is a view of the end showing a concentric pipe that directs the seawater downhill. compare to the inside of the OP's elbow without the concentric pipe.

[kenbo]

A well designed mixing elbow/injection fitting must always be designed in a fool proof way. Meaning the water must always be injected BELOW the lowest level of the exhaust manifold outlet.

The Yanmar mixing elbows are famous for corrosion on the inner dry tube where the water hits the hot dry section. The reason the manufactures supply those substandard mixing elbows is to fit into the install envelop designed by the builders at the lowest possible cost.

An earlier poster mentioned a riser built with schedule 80 pipe and a brass tee for water injection on the downside of the riser. Good concept, suboptimal execution. That's a lot of weight hanging and vibrating of the exhaust manifold, is it supported some way other than the mounting bolts?

[jimbunyard]

Your enlarged generic schematic below handily illustrates exactly how your engine can be flooded by exhaust water with no 'sucking' at all...by following seas, overloading, overcranking or unrealistic flow characteristic estimates, to name some of the more obvious failure---possibilities...

To form any opinion about the system we'd need specifics for your system; exhaust ID, length of exhaust, lift from lowest point to highest, raw water flow rate, volume of water lift muffler, etcetera. And that would only get us into a ballpark design.

While the 'system' in the first schematic will work, given the correct parameters , it is fairly dangerous and unforgiving.

Another 'solution' is shown in the doctored schematic (and the doctoring is not to scale); while it is 'safer' insofar as engine flooding from exhaust water intrusion, their is a large section of exposed 'hot' exhaust tube that must either be insulated or cooled. Both have their drawbacks; insulation actually winds up heating the engine compartment;,cooling is susceptible to clogging or conversely, saltwater leaks...

From an efficiency standpoint, if you're not familiar with the dynamics involved here, it might be advantageous to cultivate an acquaintance with someone locally who is...