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Old 05-04-2019, 04:45 AM   #1
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Wet Risers

Iíve got twin 3208NAs in an Ď86 44í Tollycraft.
I have about 3000 hours on the engines.
Short cruises a few times a year at the moment.

When I bought the boat 4 years ago, I replaced all 4 risers and all hoses. Standard Cat cast gold (I mean iron).

Any recommendations on care of these risers to slow down the need for eventual replacement?
Any thoughts on what their typical lifespan is?

Thanks,

Edward
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Old 05-04-2019, 07:40 AM   #2
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Assuming you're docking your boat in salt water, a fresh water flush may help. Boat diesel archives will likely provide details on how to hook it up on your engines. If Groco sea strainer, they offer a cap arrangement for a hose connection.

But, it can be time consuming. Some say the accelerated exhaust elbow wear occurs during operation. Will the engines, your ownership time and boat make it another 25 years?
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Old 05-04-2019, 10:29 AM   #3
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Yep. SC saltwater coast.
Have considered fresh water flushing then read pros and cons on this site and others. Maybe not as much con but sounds like thereís an argument that it may not help as much as one would think.
Still considering that though. Thanks
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Old 05-04-2019, 10:32 AM   #4
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I replaced the wet risers on my 3208NAs recently. They were built by Greenwater Marine (TX) and are a direct replacement of the cast risers. Only change was to the raw water injection hoses. See pics below
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Old 05-05-2019, 01:13 PM   #5
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Hi ORIF,

I share your apparent concern for the health of your exhaust risers. Over the years of ownership of two boats with diesel power (one with DD 671s, one with JD 6076AFM30), and upon the advice of several diesel mechanics and surveyors, I've routinely removed, cleaned, and inspected my risers approximately every five years. The has resulted in no failures (whew!), but replacements on all engines after inspection at one time or another.

Regarding your 3208NA Cats-what prompted your original replacements after purchase? How did you determine they needed replacement at that time? Seems to me, short of removing and cleaning (bead blast) and internal inspection, external inspection (unless they're REALLY bad) doesn't reveal much. So I'm curious what led you down your path?

And gsholz, same question. And gsholz, what lead you to the Greenwater solution of an insulated hot section, with the injection elbow at the top of the riser, vs the Cat stock watercooled risers? And did you, by chance, chat up National Marine Exhaust in Marysville, WA for their ideas?

For what it's worth, I've fallen into the "inspect every five years, replace after ten" philosophy regarding risers and injection elbows. Very much a routine maintenance item, in my opinion.

Regards,

Pete
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Old 05-05-2019, 02:14 PM   #6
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The big advantage of the dry risers is that no water will leak into engine when/not if/ the wet riser corrodes through. They are also self-draining, i.e. saltwater will drain from the mixer when the engine is shut down. In the wet riser saltwater fills the riser all the time.

I agree the risers are a routine maintenance item. But they are now more difficult to find and are getting very expensive. They have gone from $400 each to $1500+ each the last five years. And you need four of them in a twin engine setup.
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Old 05-05-2019, 02:43 PM   #7
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Quote:
Originally Posted by ORIF View Post
Iíve got twin 3208NAs in an Ď86 44í Tollycraft.
I have about 3000 hours on the engines.
Short cruises a few times a year at the moment.

When I bought the boat 4 years ago, I replaced all 4 risers and all hoses. Standard Cat cast gold (I mean iron).

Any recommendations on care of these risers to slow down the need for eventual replacement?
Any thoughts on what their typical lifespan is?

Thanks,

Edward
A few years back I had twin 671 Detroits that I replaced the risers on 3 times.
The last time I had stainless ones made. Canít remember the company but a Google search should turn it up.
Was thrilled when I bought my current boat (twin Cumins 5.9) it already had them on. They are stainless welded and wrapped with a ceramic tape coating.
A little pricey but worth it.
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Old 05-07-2019, 09:20 PM   #8
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Quote:
Originally Posted by jungpeter View Post
Hi ORIF,

I share your apparent concern for the health of your exhaust risers. Over the years of ownership of two boats with diesel power (one with DD 671s, one with JD 6076AFM30), and upon the advice of several diesel mechanics and surveyors, I've routinely removed, cleaned, and inspected my risers approximately every five years. The has resulted in no failures (whew!), but replacements on all engines after inspection at one time or another.

Regarding your 3208NA Cats-what prompted your original replacements after purchase? How did you determine they needed replacement at that time? Seems to me, short of removing and cleaning (bead blast) and internal inspection, external inspection (unless they're REALLY bad) doesn't reveal much. So I'm curious what led you down your path?

And gsholz, same question. And gsholz, what lead you to the Greenwater solution of an insulated hot section, with the injection elbow at the top of the riser, vs the Cat stock watercooled risers? And did you, by chance, chat up National Marine Exhaust in Marysville, WA for their ideas?

For what it's worth, I've fallen into the "inspect every five years, replace after ten" philosophy regarding risers and injection elbows. Very much a routine maintenance item, in my opinion.

Regards,

Pete
Thanks for the replies and pics bus far,

Pete, to answer your question, when I purchased my boat 4 years ago, the cooling line leading aft to the exhaust T sprung a pin hole leak. When the hose was removed, a zinc was found to have broken off and lodged in the exhaust T. The T itself was encrusted to the point that it was stenosed to a very small opening. This led to the increased back pressure and the pinhole leak in the hose.
That led to replacement of all hoses, pulling the heat exchangers and also the risers. Plan was to remove the risers and send for cleaning but internal condition was bad: broken and corroded ends and clogged shower heads.
I thought I remembered their outside appearance seeming ok but when I dug up these old pictures I'd say they looked pretty neglected externally. But still required removal of the hump hoses for full status to be seen.
Given the amount of blockage at the risers and elsewhere in the system, it's hard to understand why the engines weren't running hot.

Your idea of inspection at least every 5 years sounds like a good one.
Just curious if other than cleaning there was anything you did that you felt may have increased their longevity.
Do you recall replacing the shower heads or just having to clean out plugged holes?

I ran Barnacle Buster through the system this year being that I'm at year 4. I ran the process per spec which involves collecting the solution before the risers so there's no benefit to the risers. I considered hooking the hose up and letting the final solution pass on out through the system after letting the risers fill and pausing the circulation to let them soak. Decided against it for several reasons: environmental, might damage the lift mufflers... Anyone out there have a differing opinion/experience on whether "soaking" the risers in place could work?
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