MD2020 High Rise Exhaust Elbow

[Scubaseas]

Steve DAntonio; Big fan of your work.



Thanks for the diagram. I recall seeing those but forgot all about them. The boat owners are in Luperon, DR and not sure their portfolio will support anything more than what they have on hand. Based on diagram it looks like they'll be fine with the 70ish degree non U shaped elbow they have. They have a vented loop on the raw water side and the drop to their water lock muffler looks like there is more than enough height. Plus it looks like a big water lock. The exhaust flapper they have looks like it's out of a Raritan PH2 toilet. But if it makes em feel better, why not?

[theoldwizard1]

Originally Posted by Steve DAntonio

A check valve ahead of the raw water pump?

WOW ! DID I SCREW UP !

It is not a check valve it is a vented loop ! (Big difference, I know !)



AND it is AFTER the raw water pump !


Sorry for all of the confusion. (Thanks Steve, for catching my mistake !)

[Steve DAntonio]

Originally Posted by theoldwizard1

WOW ! DID I SCREW UP !

It is not a check valve it is a vented loop ! (Big difference, I know !)

Attachment 217999

AND it is AFTER the raw water pump !


Sorry for all of the confusion. (Thanks Steve, for catching my mistake !)

OK, good, glad to hear it.

(In Taiwan)

[jimbunyard]

Originally Posted by theoldwizard1

Video showing raw cooling water from thru-hull inlet, through the sea strainer, then the above the waterline vented loop, raw water pump to the exhaust heat exchanger. After the heat exchanger there is a waterlock, then a loop that goes well above the water line before going out.

With the vented loop and the waterlock, there is simply no need for a high rise elbow !

They added an exhaust flapper !

Just to be clear, there is nothing in the referenced video that illustrates that there is no need for a high rise elbow.

Without a detailed, preferably on-site analysis by someone who understands the dynamics of the system in question, as well as the dimensions and relations of the various parts of the system, including failure modes of those various parts and expected and acceptable ranges those parts are to be operated under, much of the advice being given here is at best speculation.

That the engine came with a high rise manifold is the best indication that one is necessary; just because it works for now without one doesn't mean it will forever -- or for long.

As for a vented loop being a 'guarantee' that "there is simply no need for a high rise elbow !", in my experience, the check valve that causes the vented loop to operate as such is just the opposite. I've repaired at least two engines because they relied on those check valves, one sunk the boat. A perhaps better solution is to remove the check valve from the loop and run a small line from it overboard or teed (or otherwise tapped) into the exhaust as it exits the hull, allowing the vent to drain naturally when the engine is shut down, Care must be taken if this approach is used since a 'trap' can render the 'anti-siphon' into a 'siphon' as easily as a clogged check valve can.


Leaving aside the complicated exhaust run, the volume of the pre-gooseneck section of the exhaust, the postion of the intake, intake and exhaust valves in relation to the waterline, and who-knows-what-other idiosyncracies of the particular system in question...

[theoldwizard1]

Originally Posted by jimbunyard

Without a detailed, preferably on-site analysis by someone who understands the dynamics of the system in question, as well as the dimensions and relations of the various parts of the system, including failure modes of those various parts and expected and acceptable ranges those parts are to be operated under, much of the advice being given here is at best speculation.

Given the fact that the boat is located in a port with A) no "expertise" in marine exhaust systems B) difficult, at best shipping C) 3 to 6 months before the existing high rise elbow could be sent to a fabricator for re-design using stainless, would you advise them to simply stay put ?

ASSUMING the waterlock and gooseneck are functioning in their designed manner, it is highly unlikely that sufficient cooling water could collect in the waterlock to rise high enough to backup into the exhaust manifold and the engine.

My advice would be SAIL ON SAILOR ! Be aware of the situation and, in large following seas, keep the engine running so that there is exhaust pressure to evacuate the waterlock and goosenck.

[Steve DAntonio]

Originally Posted by jimbunyard

Just to be clear, there is nothing in the referenced video that illustrates that there is no need for a high rise elbow.

Without a detailed, preferably on-site analysis by someone who understands the dynamics of the system in question, as well as the dimensions and relations of the various parts of the system, including failure modes of those various parts and expected and acceptable ranges those parts are to be operated under, much of the advice being given here is at best speculation.

That the engine came with a high rise manifold is the best indication that one is necessary; just because it works for now without one doesn't mean it will forever -- or for long.

As for a vented loop being a 'guarantee' that "there is simply no need for a high rise elbow !", in my experience, the check valve that causes the vented loop to operate as such is just the opposite. I've repaired at least two engines because they relied on those check valves, one sunk the boat. A perhaps better solution is to remove the check valve from the loop and run a small line from it overboard or teed (or otherwise tapped) into the exhaust as it exits the hull, allowing the vent to drain naturally when the engine is shut down, Care must be taken if this approach is used since a 'trap' can render the 'anti-siphon' into a 'siphon' as easily as a clogged check valve can.


Leaving aside the complicated exhaust run, the volume of the pre-gooseneck section of the exhaust, the postion of the intake, intake and exhaust valves in relation to the waterline, and who-knows-what-other idiosyncrasies of the particular system in question...

You really can't go wrong with a riser and a vented loop, neither are a detriment to any installation, and I always told my techs, 'if in doubt, install a vented loop', however, it should not be ambiguous, the diagrams available from most engine manufacturers are very clear, this is one of the better ones I've seen https://www.northern-lights.com/medi...t_drown_me.pdf Note the third diagram, engine below WL, riser above, no vented loop.


If the engines and injected elbow are, or must be below the WL, then you need a water lift muffler and vented loop, and if in doubt, again, install one.

I completely agree, removing the valve in a vented loop and plumbing the vent overboard (where it can never be obstructed, kinked or submerged) is the most reliable approach. Few vessels use this approach, but it is absolutely valid. ABYC Standards do prohibit pluming any "drains" into an exhaust, so I think I'd avoid that approach. I like the idea of being able to see water come out of it while the engine is running.

(In Taiwan)

[theoldwizard1]

Originally Posted by Steve DAntonio

If the engines and injected elbow are, or must be below the WL, then you need a water lift muffler and vented loop, and if in doubt, again, install one.

The installation in this discussion HAS a vented loop and it HAS a waterlock. The only discussion is if they need a high rise exhaust elbow in addition to those items.

[Scubaseas]

If they want to keep the loop in the outlet of the HX they should be able to locally source a stainless hydraulic street elbow. They may have to grind off or cut down about 1/4" off the female threads on the mixing elbow they have but there should be enough room to fit a hose on the mixing elbow and rotate the HX end cap 180* and use a length of hose to duplicate the high rise they took off. Any place that makes hydraulic hoses should have a street elbow. I am aware they are in Luperon, DR.



Hard to say without knowing exactly where their waterline is at but it looks like they should be fine with what they have. I am guessing their waterlock is a two gallon model. The design on the system they have is fine per the Volvo install specs supplied by Mr. D'Antonio depending on where exactly the water line is. The amount of water left in the water lock after they ran the motor didn't seem to be an appreciable amount relative to the capacity of the waterlock.

[theoldwizard1]

Originally Posted by Scubaseas

If they want to keep the loop in the outlet of the HX they should be able to locally source a stainless hydraulic street elbow.

Their biggest concern is that any water in the waterlock could back up into the exhaust manifold and into the engine. Makes me wonder with there is not a flapper (one way valve) just inside the waterlock inlet, but I suspect the issue is that it would be a "wear item" and if it broke off could cause a bigger problem.

Originally Posted by Scubaseas

The amount of water left in the water lock after they ran the motor didn't seem to be an appreciable amount relative to the capacity of the waterlock.

Another "advisor" suggested that there would be a quantity of water in the waterlock that could slosh into the exhaust manifold when the engine is off and they have a following sea. My recommendation in those sea conditions is to run the engine. Exhaust pressure will keep the water in the waterlock to a minimum and also prevent it from traveling up the the exhaust hose.

IMHO, the high rise exhaust elbow is "belts and braces". A good idea, but not necessarily critical. These cruiser have decided to stay in Luperon, DR until the end of hurricane season, so if want to go the "whole 9 yards", they can ship the old elbow back to the US to someplace that specializes in making such items and have one fabricated out of stainless.

[Scubaseas]

Have Joel measure where the waterline is and compare his installation with diagram. It's either good or it's not. He can take off the hose to the vented loop and lower it until water comes out to establish the water line.



There is no mechanical flapper in a Vetus LP muffler. Keep in mind the silencer they way at the stern will also act to deter water entry. I get the slosh bank up into the engine but again if he measures it and it's OK, then it's OK.



I would be careful running the engine just to keep water out. There are heel angles that effect oil pressure.



A new stainless high rise would be nice but it may not be necessary and not sure their portfolio could support it.

[Scubaseas]

Vetus diagrams/specs. I believe these are what they have.



http://www.vetusmarine.com/Shared/PDFs/Page%2068.pdf


http://www.vetusmarine.com/Shared/PDFs/Page%2070.pdf

[theoldwizard1]

Originally Posted by Scubaseas

Have Joel measure where the waterline is and compare his installation with diagram. It's either good or it's not. He can take off the hose to the vented loop and lower it until water comes out to establish the water line.

Great suggestion !

Originally Posted by Scubaseas

There is no mechanical flapper in a Vetus LP muffler. Keep in mind the silencer they (have) way at the stern will also act to deter water entry. I get the slosh back up into the engine but again if he measures it and it's OK, then it's OK.

There is always going to be "some" water in the waterlock from the inlet side. The questions are "How much ?" and at "What angle ?" would the stern have to be in relationship to the bow for that amount of water to go up into the exhaust manifold and engine.

Originally Posted by Scubaseas

A new stainless high rise would be nice but it may not be necessary and not sure their portfolio could support it.

Tough call and these people do live like paupers ! They could use some more solar power and a couple more batteries.

[Scubaseas]

https://www.cruisersforum.com/forums/attachment.php?attachmentid=217922&d=1592881129

Courtesy of Steve D'Antonio.


As long as they are within the specs on #9 they're good.

Vetus install sheet see pages 14-16 https://www.vetus.com/media/magentominds/sasdocument/20200615094047_0.pdf

"What angle ?" would the stern have to be in relationship to the bow for that amount of water to go up into the exhaust manifold and engine.

Probably about 20* beyond when they would be pitch poled anyway? I wouldn't worry about it much if you meet specs.

Seriously as long as they meet the install specs for Volvo and Vetus they are fine.

How much does it cost to cruise? Whatever you have!

[Steve DAntonio]

If you have the engine manufacturer required drop between mixing elbow/riser and water lock muffler (usually a min of 12"), and the correct down angle if specified (some are a min of 15, others 25 deg, others don't specify, but the closer to vertical to better) you won't have an issue with water going the wrong way. There are rare exceptions but in nearly all cases there are no check valves inside mufflers, and they are not necessary. The problem with in line exhaust check valves is they fail or disintegrate, and you have no way of knowing it. A flap on the overboard discharge does make good sense, if you you have a stub, at least you can monitor it.

[theoldwizard1]

Originally Posted by Scubaseas

https://www.cruisersforum.com/forums/attachment.php?attachmentid=217922&d=1592881129

Courtesy of Steve D'Antonio.

As long as they are within the specs on #9 they're good.

Originally Posted by Steve DAntonio

If you have the engine manufacturer required drop between mixing elbow/riser and water lock muffler (usually a min of 12"), ...

The Volvo spec in #9 of the above link shows 8" from the bottom of the exhaust manifold inlet (NOT the bottom/lowest point of the elbow) to the water line.



EDIT : (if I have not forgotten all of my engineering skills) an 8" column of water in a 1.75" ID pipe is over 2 quarts of water ! Assuming no water is getting up past the gooseneck between the waterlock and the exhaust thru-hull, that is a lot of raw water from the raw water pump that has not been pushed out by the exhaust !