Exhaust elbo

[Mlm2]

I Think the current configuration of this connection add some stress to the boot due to the vibration of the hose. The boot has failed twice within 300 hours of operation. The way it is now makes it easy to service the tube stack, but when it ruptures it makes a mess in my engine room. Looking for recommendations or photos of your setup.
The engine is a Perkins 6.354 with a manicooler.

 

[kchace]

I have a vented loop there with a small bracket for support. Works great. Those end caps should last many years.

Don’t know why the picture is sideways but if you click on the picture it will open in a new window right side up.

Ken

 

[kapnd]

If the boot ruptures, the shower head in the elbow is likely plugged.
It looks like the hose exiting the reducer boot may be kinked as well, or is that just a shadow?

 

[Mlm2]

Just a shadow. The boot is new. The last one ruptured just in front of the smaller clamp. When the engine is running the loop vibrates and I thought that would stress that part of the boot. I have seen on setup where the elbow intake was straight back and a small connection hose was used..no vibration

 

[kchace]

Vibration in that loop would definitely stress the end cap. If the loop is there to gain height to prevent siphoning then you should also install a anti-siphon vent (see the pic I posted above). If it’s not needed, then you could change fittings to allow a straight hose and not a loop. Also, heavy hose is not needed there as there should be almost no pressure there and by definition it should be above the water line. Good quality heater hose type hose is quite sufficient and would put less stress on the end cap.

Ken

 

[Mlm2]

I would like to put a piece of straight hose on, but I'll have to try to tighten the elbo to move the hose connection further to the left ( in photo). The photo is of the ruptured boot and why I asked the original question

 

[Mlm2]

Guess what happened. Emergency repair 5 miles out. I need to change something!

 

[Bmarler]

Agreed. Something needs to be done. I don’t like the big loop of heavy hose being unsupported like that. Even if all you did was make a bracket to hold that hose so it didn’t put any tension on the reducer.
That alone should take care of it.

 

[Mlm2]

Here´s the update. I removed the elbow and found the water inlet almost completely corroded shut. I replaced the elbow with a stainless steel one and eliminated the loop.That should solve my issue.

 

[kchace]

The 31 year old original elbows on my boat were also almost completely blocked internally. This had the effect of highly pressurizing a system that should have very little pressure. I realized it when I saw the hose to the elbow bulging during an underway check. It looks like you installed a stainless elbow from Trans Atlantic Diesel. I have just replaced both of my main engine elbows with the same. The quality and fit is excellent.

Ken

 

[Larry M]

I don’t see a vented loop anywhere. The “loop” you had before may have served that purpose. Google “marine engine vented loops”. The one below was one of many. I don’t profess that I know about vented loops but every marine diesel we’ve owned and the boats I’ve worked on, all had one. Kchase’s post has one.

A vented loop (also called a syphon break) prevents raw water being sucked through the raw water cooling circuit, into the muffler and then back-flooding into the engine when the engine is stopped. The valve at the top of the loop allows air to flow into the hose thus breaking the syphon.

 

[Mlm2]

Larry, the loop before had no vent. The 3 inch exhaust hose from the muffler has about a 30 inch drop to the back before exiting the boat.
Not sure I would need to add a vent.

 

[kchace]

Larry, the loop before had no vent. The 3 inch exhaust hose from the muffler has about a 30 inch drop to the back before exiting the boat.
Not sure I would need to add a vent.

Can’t comment on your exact exhaust config, but it’s not how far the exhaust drops after the muffler that matters. A vented loop ensures the exhaust injection water does not siphon through the engine during shutdown. This would fill the muffler until it was able to back flow into the engine. It’s all related to how high the external water level is in relation to the exhaust elbow. I have seen some diagrams specifying a minimum of 6” lower than the exhaust elbow, but more often I have seen a spec of 12” minimum or else a vented loop is needed.

Ken