Water Injection Elbow

[Celestialsailor]

Does anyone know how easy it is to make a water injection elbow for the exhaust? What I've got now is some Rube Goldberg affair. It just seems that they are an elbow with a pipe welded down into them pointing downstream. Does anyone have direct knowledge and not just speculation?

[SkiprJohn]

Aloha Martin,
I can provide a photo of mine. It is a stainless 2" pipe with 30 degree or so bend with a 1" pipe welded on it pointing down hill much as you described.
It's been so long since I got it that I can't remember what I paid to have it shipped.
Here's a factory photo of the engine with the injection elbow coming from a Bowman heat exchanger.

[Celestialsailor]

Thanks John...What I currently have is a funky 4 bolt flange to a flexible bellows type SS tube. You can guess how long that will last! So I will buy a 45 degree elbow and weld a 1" downhill tube into it. As you can guess...I just got the engine back.

[Target9000]

Originally Posted by Celestialsailor

Thanks John...What I currently have is a funky 4 bolt flange to a flexible bellows type SS tube. You can guess how long that will last! So I will buy a 45 degree elbow and weld a 1" downhill tube into it. As you can guess...I just got the engine back.

What kind of motor is it? Our boat had a Perkins M50 in it with a four bolt flange into a flex pipe then a water injection. The one on the motor lasted 20 years. From the looks of how it was made, no back siphoning could ever occur.

The spare looked like this:

[russcannell]

The only problem you will find is that above the water injection bend the exhaust will be at a temperature that could cause a fire. A number of manufacturers specify a double wall injection bend that goes right up to the manifold. This keeps the full exhaust system cool. If you fit a single wall bend with an injection feed, then you need to lag the upstream part of the exhaust manifold. This is the reason why the correct part is so expensive.

[Target9000]

On our new motor with a factory high rise exhaust you can see the setup in this photo:

[DeepFrz]

Don't forget the siphon break and it is always best to have an upward bend in the exhaust and then downward before the water injection. As mentioned above and shown in the picture, the exhaust from the manifold to the injection port must be lagged.

There are a number of threads on this forum that describe in detail how people have built injection elbows.

[Celestialsailor]

Originally Posted by russcannell

The only problem you will find is that above the water injection bend the exhaust will be at a temperature that could cause a fire. A number of manufacturers specify a double wall injection bend that goes right up to the manifold. This keeps the full exhaust system cool. If you fit a single wall bend with an injection feed, then you need to lag the upstream part of the exhaust manifold. This is the reason why the correct part is so expensive.

What do you mean by lag? My Yanmar was not double wall or my Perkins or Volvo.

[Celestialsailor]

Originally Posted by DeepFrz

Don't forget the siphon break and it is always best to have an upward bend in the exhaust and then downward before the water injection. As mentioned above and shown in the picture, the exhaust from the manifold to the injection port must be lagged.

There are a number of threads on this forum that describe in detail how people have built injection elbows.

Much like Targets picture I assume

[Celestialsailor]

Originally Posted by Target9000

What kind of motor is it? Our boat had a Perkins M50 in it with a four bolt flange into a flex pipe then a water injection. The one on the motor lasted 20 years. From the looks of how it was made, no back siphoning could ever occur.


The spare looked like this:

Yes...the flex bellows looks like that. The one in the picture lasted 20 years? My engine is a Mitsubishi based Westerbeke W46

[DeepFrz]

Much like Targets picture I assume

Yes. I'm not sure of the need for the bellows type section if the hose from injection elbow to muffler is flexible, and I'm sure most are.

[Tingum]

If you are in the process of making one use aluminium rather than stainless. Stainless tends to corode through where the salt water hits the hot metal.

[Target9000]

Originally Posted by Celestialsailor

Yes...the flex bellows looks like that. The one in the picture lasted 20 years? My engine is a Mitsubishi based Westerbeke W46

No, this is a spare that was on board when we pulled the old motor, but there was one attached to the motor that was near identical. I went through the ship's maintenance log and saw that it had been installed in 1992 and lasted until 2011. There was mention of pulling it apart once to clean it out but it was re installed and the spare never mounted.

[rtbates]

what you and nobody else can SEE is the double wall tubing with the exhaust in the inside tube and the water injection tube in the outer tubing... The exhaust or inside tube doesn't go too far past the exhaust manifold, JUST FAR ENOUGH. Without this feature the exhaust tubing up at the manifold will run JUST SLIGHTLY cooler than the exhaust manifold ON YOUR CAR<<<< HOT HOT HOT

[Blue Stocking]

Originally Posted by Target9000

No, this is a spare that was on board when we pulled the old motor, but there was one attached to the motor that was near identical. I went through the ship's maintenance log and saw that it had been installed in 1992 and lasted until 2011. There was mention of pulling it apart once to clean it out but it was re installed and the spare never mounted.

My W46 is similar except that the last elbow before the T, is a tee with reducing bushings, and a welded thru nipple, long enough to exit the water at a lower point than the horizontal section. My Vetus vent is high up under the cockpit seats.
The weight is supported by a hung rubber strap, to the underside of the bridge deck