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Old 18-05-2020, 10:13   #1
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Wet muffler/mixing tank combo replacement - Perkins 4.236

I noticed the combo wet muffler/mixing tank on my boat is beginning to leak. The boat uses a Perkins 4.236 diesel. Attached are some photos of the set up, which appears to be a unique set-up for this vessel.

The muffler has three ports, engine exhaust in at the bottom, salt water from the heat exchanger in from the top and the combo exhaust out about 1/2 way up. It is situated vertically, at about waterline directly behind and above the motor in an engine room of sorts. I can get measurements for each port next time I'm at the boat this week.

Centek Marine let me know that their FRP tanks are all for post mixing elbow set ups and this mixing tank/muffler combo is not something they can accommodate.

Any idea on who I can contact for a replacement?

Also any ideas for a temporary patch solution for the leak in the mean time?
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Old 18-05-2020, 10:24   #2
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Re: Wet muffler/mixing tank combo replacement - Perkins 4.236

JB Weld should patch it. You could put a screen door screen material in the JB if it's a large hole.
Usually the cooling water just goes in the exhaust hose first. I wonder why you cant just do that and use a normal fiberglass waterlift muffler...? It appears you must have a rigid metal exhaust pipe from engine to muffler as a hose would burn.
Also, it's likely that the exhaust inlet in yours at the bottom is actually a tube that extends up high in the housing... not just a bottom inlet.
You could also just add the cooling water fitting to the top of a standard muffler I suppose. But it would be nice to get rid of all that insulated exhaust pipe and use a cooled hose ..


Also, it's not real hard to make your own custom fiberglass muffler. I have made a couple. Buy fiber glass elbows if needed. Layup a tube over a cardboard tube or whatever you can use as a form, etc... But far easier to just buy a ready to use one.
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Old 18-05-2020, 10:48   #3
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Re: Wet muffler/mixing tank combo replacement - Perkins 4.236

Thanks for the advice. It appears all the other DE45 owners (and there aren't many of us) I've asked about the problem all have a different set up.

I'm waiting for some pictures, but I'm guessing they all have a mixing elbow to water lift muffler set up. Perkins still makes mixing elbows for the 4.236 and there are countless water lift options so I could definitely fidn something that would work. But it would require replacing the whole system, which I'm hoping to avoid.
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Old 18-05-2020, 11:11   #4
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Re: Wet muffler/mixing tank combo replacement - Perkins 4.236

I am going to try to talk you into converting to a now-current exhaust system with mixing elbow. I realize you want to avoid this, but long term, keeping your run of un-cooled exhaust will reduce heat, reduce wear, be more compact, and reduce weight. The only downside is initial expense to make the swap. Transaltantic Diesel (TAD) sells a decent SS mixing elbow. Marine Exhaust Systems of Alabama (Mesa) can fabricate to your spec.

Decent article on exhaust design from Steve D'Antonio

If you're set on replacing with a metal tank, you might want to search for someone who makes boiler tanks.

Good luck!

Peter
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Old 18-05-2020, 11:29   #5
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Re: Wet muffler/mixing tank combo replacement - Perkins 4.236

Thanks Peter, it is definitely on the table. Hopefully I can get the pictures from the other DE45 owners on their set ups so I can figure out where to situate the new lift muffler, etc.
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Old 18-05-2020, 18:04   #6
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Re: Wet muffler/mixing tank combo replacement - Perkins 4.236

Quote:
Originally Posted by mvweebles View Post
I am going to try to talk you into converting to a now-current exhaust system with mixing elbow. I realize you want to avoid this, but long term, keeping your run of un-cooled exhaust will reduce heat, reduce wear, be more compact, and reduce weight. The only downside is initial expense to make the swap. Transaltantic Diesel (TAD) sells a decent SS mixing elbow. Marine Exhaust Systems of Alabama (Mesa) can fabricate to your spec.

Decent article on exhaust design from Steve D'Antonio

If you're set on replacing with a metal tank, you might want to search for someone who makes boiler tanks.

Good luck!

Peter
@ Peter, that was a good article, thank you.
@MDR, I am sure you can repair/reweld your exiting setup. But long term, you may consider mixing your seawater higher up. TAD diesel sells them for various exhaust manifolds, or buy a new SS exhaust manifold, see this link: Perkins Exhaust Elbows | Perkins Stainless Steel Exhaust Elbows | Perkins Flanges | Perkins Diesel Parts. I don't know prices, but I am sure multiple $$$.
If you are handy, make a waterlift muffler from fibreglass, to fit your space, never rusting anymore. I have a 4.236 as well, but my waterlift muffler is SS, rectangle box, is 35 years old and as new (opened an inspection hatch to check the internals a week ago).

Your Downeaster, does that have a schooner rig? Nearly fell for one a few years ago, loved the aesthetics.
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Old 18-05-2020, 18:16   #7
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Re: Wet muffler/mixing tank combo replacement - Perkins 4.236

Thanks Hank! The current system mixes about 3ft above the motor and ~2ft above the waterline, which is about as high as I could feasibly get it on this boat. It's one reason the current set up is appealing, since it basically eliminates the chance of seawater getting back into the motor.

If I replace with the lift muffler set up I'll still likely end up with some dry exhaust lifter to keep the mixing high up.

My DE45 is the cutter rig, which was a big selling point for me. They only made ~28 of the 45s and there seems to be a pretty even split between cutters, schooners and ketches. She sails very well in lighter winds (for 20 tons that is) and is steady in heavy weather.
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Old 18-05-2020, 18:41   #8
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Re: Wet muffler/mixing tank combo replacement - Perkins 4.236

If your manifold exit is indeed 2-feet above waterline, you do not need a siphon break. But that is pretty high, especially on a sailboat. As a comparison, mine is about at-waterline.

A decent SS exhaust elbow with mixing inlet is in the $800 range from TAD (I think) for a standard 45-degree downturn (I think). Custom will run closer to $1500. I just purchased a Cetrex lift muffler for my 4.236 (3-inch). I think it was in the $200 range. 3-inch hose is expensive.

Really depends on how you plan to use the boat. The hose and fiberglass fittings will last a very, every long time as long as you don't run the engine dry and start running 900-degree exhaust through the system. Folks say the mixing elbow is 5-7 years, but in reality, it's a few to several 1000 hours.

In my opinion, exhaust systems are a really bad place to save money. You can through a bunch of stupid money at them and over-spend, but there are some basics to get to an acceptable system where I would not skimp.

Peter
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Old 18-05-2020, 18:50   #9
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Re: Wet muffler/mixing tank combo replacement - Perkins 4.236

@Peter - The manifold exit is about 1ft below waterline, but the exhaust and raw water do not mix until 2ft above the waterline. There is no traditional mixing elbow off the manifold, it is insulated metal pipe that enters the muffler/mixing tank dry at the bottom, raw water exits the heat exchanger and runs through ~5ft of hose until it enters the top of the muffler/mixing tank. It mixes somewhere in that tank which is about 2.5ft tall before exiting at a midpoint into 3" exhaust hose.
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Old 18-05-2020, 19:08   #10
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Re: Wet muffler/mixing tank combo replacement - Perkins 4.236

Quote:
Originally Posted by MDR_Sailing View Post
@Peter - The manifold exit is about 1ft below waterline, but the exhaust and raw water do not mix until 2ft above the waterline. There is no traditional mixing elbow off the manifold, it is insulated metal pipe that enters the muffler/mixing tank dry at the bottom, raw water exits the heat exchanger and runs through ~5ft of hose until it enters the top of the muffler/mixing tank. It mixes somewhere in that tank which is about 2.5ft tall before exiting at a midpoint into 3" exhaust hose.
Okay. Please don't take this as gospel. I'm pretty knowledgeable but not an expert.

Back in post #2, Cheechako included a diagram. Bottom is what you want. Because your engine is below waterline, you will need a vented loop as shown.

The reason for the high loop after the lift muffler is to prevent casual water back into the system. This would come from hobby horsing at anchor and scooping water into the exhaust and eventually filling the line.

The Cheechako diagram shows a stock Perkins mixing elbow (no detail, but that's what would work). There is a school of thought that instead of exiting the manifold and going down to the lift muffler, it should turn directly up to above waterline, then make a near-180 degree downward turn. Water mixed at the downhill side of this 180 degree turn so everything from manifold to water injection is a custom elbow. This gets expensive - $1500 and up. Benefit is that if this loop is higher than the second loop after the lift muffler, your engine is pretty safe from raw water damage. But it takes a lot of space, generates some heat, and is relatively expensive. If I were headed off for serious cruising, I would not hesitate to spend the dough. This is not a place where you want to cheap out. But if you're a weekend warrior, would not worry too much.

BTW. Best if exhaust through hull is centerline on transom. Probably is already, but just wanted to mention.
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Old 19-05-2020, 13:39   #11
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Re: Wet muffler/mixing tank combo replacement - Perkins 4.236

I took my old leaker out and gave it to a welding shop that does work for commercial fisheries. New one built of stainless steel and has been in the boat 14 years now. 100 bucks.
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Old 20-05-2020, 23:41   #12
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Re: Wet muffler/mixing tank combo replacement - Perkins 4.236

Usually the reason there is a exhaust system like you have [ i have the same] is because there is NO room for a water lift, either vertically and or horizontally, mine rotted out, and i had a Stainless steel replacement fabricated, it wasn't that much.
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Old 23-05-2020, 09:02   #13
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Re: Wet muffler/mixing tank combo replacement - Perkins 4.236

My friend with a Cal 35 cruiser has the same exhaust setup on his 4-107. You might want to see what the Cal crowd thinks. I would take it to a welding shop and have the fab one up. Not sure stainless is required as that on is probably pushing 40years before it leaked.
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