Exhaust Type?? For Engine Off Flushing

[Matt Lyman]

I have a GB 2008 EU 47 with QSC 8.3 and I’m trying to figure out what type of exhaust I have so I can hopefully install an engine-off fresh water flush system. It doesn’t look like a lift muffler at all (which I know you can’t use for engine off flushing).

What type is it?

See any issue with engine off flushing?

It’s all downhill from the raw water inlet to the exhaust, and the 3” diameter pipe off the muffler is above waterline. The main exhaust discharges out the bottom of the hull

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Thank you for the help!

Topic

[Tony Athens]

You are obviously on a mission. Allot not less that 25 gallon per flush. Then, you really need to “taste” what you got to be sure at a minimum..

[Matt Lyman]

Solution?

– Yes, I’m asking about draining the water prior to the mixing elbow, thus bypassing the lift exhaust for engine-off flushing. Similar, but permanent to a descaling hookup. Engines would be off.

– I have a fresh water spout in the engine room. I can easily and permanently plum it to the raw water line after the seawater pump, per Tony’s specs for engine-off flushing. Once hooked up, all I’d have to do to flush is turn a valve before the seawater pump (for freshwater inlet), a valve before the exhaust (for discharge), and turn the fresh water on. All with the engines off.

– BTW. I would not drain into a bucket, that’s not realistic. I would drain into the bilge to be pumped overboard by the bilge pump.

– My option, once setup, seems easier to me (and thus I’d be more likely to do it) then dragging a hose in and out to my strainers (which are hard to get to), reaching the seacocks, or filling a freshwater bucket, then running up and down from the engine room to the ignition trying to time shutoff before the bucket goes dry, all while trying to reach the seacocks.

Thoughts on the idea?
One other odd question – Approx How much water do you think is in the raw water system of a QSC 8.3? Anyone ever measure?

– See attached drawing.

Thank you everyone.

[Gene Fuller]

My point was that a flushing system will not get used routinely if it is difficult or awkward.

Descaling into a bucket once in a while is one thing. Flushing into a bucket after every trip is way too much trouble.

Gene

[Dan]

Matt,
Apart from what others have mentioned (and if I’m understanding you correctly) are you proposing to run the engine with out water running through the exhaust system?

The exhaust system is raw water cooled.

[Rob Schepis]

What you are proposing is along the lines of setting up a descaling flush where you capture your discharge. Clearly more complexity to the setup and more steps involved in using it but it could work.

[Matt Lyman]

Thank you for everyones input. I totally understand the issue is after the mixer with the type of exhaust I have, which is why I was asking about draining beforehand, out the raw water discharge of the engine before it hit the mixer per my drawing.

[Tony Athens]

IMO., our Mr Lyman, does not understand the it issue is AFTER the mixer……………………….Flat out, hands down the engine need to be running if he wants to flush “safely” with the design of his exhaust system..

Tony

[Steve Lewis]

Matt,

I think you are getting your answer. Indirectly as it may seem. Re-read Rob Schepis’ answer completely and carefully. Gene even chimed in with his “I can’t image” comment. If you are still in doubt, re-read Tony Athens’ answer. I heard/read somewhere that he knows what he is doing and recommending………..

Rob appears to be questioning the idea of placing a water exit valve in the Exhaust system. When you shut down, are you absolutely sure that you would have the valve in the right place and do you really want to deal with the HOT side of things when doing this flush? It seems that you have your “Too Risky?” answer.

You are getting Best Practice recommendations on how to FWF from this forum. Any deviation from best practice is more of an “At your own risk” proposition.

[Matt Lyman]

Thank you everyone, but I’m well aware of ‘engine on’ flushing through the seawater strainer. Thats really not my question. See my post above. Or to reiterate:

What are you thoughts on putting in a T with locking valves on the engine raw water discharge and going into the bilge for engine off flushing and avoiding the lift muffler? See pic/drawing. Too risky?

[Mike Uliasz]

Check out the Tony’s tips video:

The Benefits of Fresh Water Flushing your Marine Diesel Engine

Use the intake strainer flush like Gene mention. Straight forward, no special connections. You could even hook it up to the fresh water hose if you have a fresh water connection in your cock pit that pulls from the fresh water tank and close the raw water intake. Be low volume water. I hook up to the dock water, leave the raw water intake valve open, since the strainer will get back flushed too.

[Gene Fuller]

If I can’t flush and discharge into the mixing elbow/exhaust

Lots of people do exactly that. Just run the engine while flushing. I would guess that the majority of “flushers” have water-lift mufflers and need to run the engine while flushing with fresh water.

I cannot image anyone seriously trying to routinely flush and capture the water in a bucket.

One of the most common methods is to introduce the water at the intake strainer. I use that method routinely. No problem at all, and I do not have engine controls in the engine room.

Gene

[Pequod]

Install a switch on the engine to the run (stop) solenoid.

[Matt Lyman]

Thoughts on this?

Thank you everyone for your help and input. I too learned something!….. however I’m persistent in my quest for engine-off flushing for a ton of reasons, the first few being:

– So I can rig up a fixed system and flush from my fresh water tank and the spout I have in the engine room.
– Because I have no engine shut off in the engine room, so I can’t watch an engine drain a bucket I’d have it pull from and kill the engine in time.
– Because I know the easier it is, the more likely I’ll do it regularly.

If I can’t flush and discharge into the mixing elbow/exhaust, what are you thoughts on putting in a T with locking valves on the engine raw water discharge and going into a bucket or the bilge? See pic/drawing. Too risky?

[Woo]

Wonderful explanation Rob, thanks for taking the time to explain it. Learnt something today…… 🙂

[Rob Schepis]

Inline Lift Muffler

You need to understand what is inside this inline lift muffler AND understand the physics as to what goes on during a startup.

Look at the sketch.. The running level of this muffler has about 3-4″ in the bottom of it (hopefully not more). Lots of air volume to allow the engine to start safely (remember air compresses, water does not)

Engine off and flush. The water will fill up to a very unsafe zone before it “finds its way out” as you said….

Do we really know the static water line of the vessel inside the output tube in the bottom of the boat? I don’t nor would I guess, but the system, to be safe totally relies on that.

Do you really want to start the engine with the exhaust gases and water having no place to go and take that chance? Not me…

As to the system in general? On the scary side to me, but he does have a decent riser – That would be the only thing in the system that protects it.

It would be interesting to see an exhaust pressure measure graph.

3 users thanked author for this post.

Woo, BrisHamish, Tony Athens

[Woo]

Excuse my ignorance but how do well tell Tony? To my eye it looks like an underwater exit muffler with internal baffles and a 3″ relief port exiting above waterline for engine starting.
If fresh water was injected aft of the mixer, would the water not find its way out the relief port at minimum, and probably out the large underwater exit as well due to gravity? The mixer is clearly well above the muffler. Genuinely interested to know this.

[Tony Athens]

You have an inline lift type muffler————-You need to do your flushing with the engine running.. That’s ippso-facto

[Matt Lyman]

Sorry, I have no idea why two of them posted upside down.

[Matt Lyman]

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