flexible wet exhaust pipe

psneeld said:

Sorry...you are correct...just before the injection would be best but not always possible.

I'm thinking of moving mine...just got to alter a few things..

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I haven't attached mine yet, but Borel's instructions are:



Some have mentioned that there can be a hot spot at the top of the hose, just down stream from the mixer elbow at low engine speeds. Apparently there is not enough 'mixification' (new nautical term) and the water is just running down the hose in a stream, which keeps the bottom cool, but allows the top to become hotter. Because of this, false alarms can occur. In this case, they recommend placing the sensor(s) along the bottom of the hose.

psneeld said:

I'm thinking of moving mine...just got to alter a few things..

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Mine is an old Aqualarm made of CPVC good for 250F they said, so I moved mine.

HopCar said:

I'm familiar with the Trident 252V hose that has been recommended. It really is great hose. If my memory is correct it can be had in 3, 6, 12 and 60 foot lengths.
I also know a Trident distributor with great prices who ships to Oz, but the forum rules prevent me from saying who it is.

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But I can I believe.

Try contacting these fine folks: Hopkins-Carter Marine Supply and Fishing Tackle

Thanks Bill! He did!

As I've already pulled the system apart (thus cannot run my engine to find out) - can anyone gove me a ballpark figure of what temps I'd be looking at that close to the water injection? The discovery of the trident Extreme temp hose (thanks Parks!) has me wondering if I shouldn't go up to that rating (rather than the 'standard' high temp hose rated to 180 deg C).

So.. if anyone can help with those temps I'd be mighty thankful.

Cheers!

shufti said:

As I've already pulled the system apart (thus cannot run my engine to find out) - can anyone gove me a ballpark figure of what temps I'd be looking at that close to the water injection? The discovery of the trident Extreme temp hose (thanks Parks!) has me wondering if I shouldn't go up to that rating (rather than the 'standard' high temp hose rated to 180 deg C).

So.. if anyone can help with those temps I'd be mighty thankful.

Cheers!

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For decades in both gas and diesel, I have always heard that you should be able to rest your hand on the riser or hose when running at cruise or <140F. The exhaust hose on my Yanmar 4JH3E runs about 110F in the summer and a little cooler in winter. On my old Donzi, with a Mercruiser 525SC the risers and hoses were only warm to the touch. We always checked the risers by hand and never had any unpleasant surprises. Lucky I guess.

Borel and Aqualarm use temperature sensors that activate in the 175-200F range for their cooling water alarm system.

Maybe some other TF members have experience they can share.

Larry
M/V Boomarang

Thanks Larry. Wow - that's kind of surprising to me - I never would have thought the exhaust could be cooled that quickly. This is my first wet exhaust system - I'd never even consider touching a dry system pipe. I suppose there's a fair bit of water being pumped into it - but even so... quite amazing.

Thanks all for the input - it's been very interesting.

shufti said:

I'd never even consider touching a dry system pipe. I suppose there's a fair bit of water being pumped into it - but even so... quite amazing.

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Yes, a dry stack is a very different beast. Why don't you post the exact engine(s) you have in your boat so others might chime in with their observations.

BTW, I believe that standard black marine exhaust hose is rated at 250F, which is well above the overheating thresholds established by the alarm manufacturers. Many thousands of boats are equipped with standard hose, and run for a very long time with the original hose(s) installed by the builder or rigger.

I would use blue or red silicone hose if you have an application that requires it, or if you simply want the extra capability and durability, or even just for the cool factor, but most applications will be just fine with standard hose. I only used it in my application because I needed the flexibility of the corrugated silicone hose, and I found a remnant that was half price.

Larry
M/V Boomarang

They are Volvo TAMD41A's, Larry.

I got a good deal on some purosil hose from a guy close by today - so I'll be sporting nice new cool factor blue pipe

Looks like standard black hose on your original install, if that did not burn out it should be fine. Normal wet exhaust runs maybe 40F above sea temp, but there can be hot spots.

That's a tight 90deg bend right at outlet, that may be tricky to make that bend.

I'm going to cut the [strait] rusty middle out and use the [ok] end bends. The pipe I put in will run strait.

>The obvious best sensor in my cases would be an exhaust temp sensor.<

And then you can hire someone to watch the gauge 100% of the time?

Or simply install a Murphy Switch Gauge and respond to the alarm IF it goes off.

Update - Purosil hose delivered for $220.

On closer inspection, none of the original tube is worth using. Looks like rusting is at each weld, not even 316 stainless to start with. A few more SS fabricator quotes saw estimated labour times ranging from 1 to 7 hours. Spoke to a couple of F'glassers today and have decided to go that route for the elbows. Around $200 for both of them using the original pipe to make the mold.

Is it worth getting the glass guy to make an extra set up (for future 'just in case') or is it just as easy down the track to get replacements made using the ones I'm getting made now? What do you people think?

Are the angles not 90 deg.? Because you can buy stock 90 deg. fiberglass exhaust elbows.

If you have custom ones made make sure they use fire retardent resin.

There are multiple angles in the bend aft of the water injection elbow. The end at the muffler is 45. Yes I could have used pre-made bends plus a 'hump' fitting - but this will [should] be an exact fitting for around the same price, and in my hands in about the same time as a delivered item.

And, yes, using the appropriate resin.

shufti said:

. . . using the original pipe to make the mold.

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Hmmm, wonder how he intends removing the rotten stainless bits from inside of the new fiberglass - cutting lengthwise and sticking it back together? Or maybe just using the old one as a pattern? Not intending to leave it in there I hope.

I would only make one unit - it should last almost indefinitly.

Please post pics as you go.

Using the original SS to make a mold, then using the mold to make the final elbows. So not leaving the pipe inside The pipe is more rusty on the inside anyway - the holes that developed were still pin-prick stage - I caught it just in time.

Will post pics.

Just picked up the f'glass elbows. They definately look the business. Very happy with the end products. Ended up being $260 for the lot. Now to get down to the boat and put it all back together. I'll get some pics down there.

BTW - gotta give 'Bundaberg Fibreglass Services' a plug. Great service, end product looks great plus they got the job done earlier than quoted so I could go fishing this weekend Legends!

Just a quick update. Put the new section in - all good. Started motor and spent 5 minutes nipping up hose clamps and all drips vanquished. Thought I shold probably run the s'board motor as well as neither had been kicked over in about 3 weeks. Sat in the eng room admiring my handiwork when I noticed water coming from starbord exaust hose (somewhere stern-side of the muffler).

Cockpit floor now out and full exhaust re-fit operation in place at present. Yay Boats!

How about a picture?

Same Engine Here

It sounds like you have it figured out. I have the same engine in my boat. Mine is the metal reinforced rubber type in the exhaust run in question.

Sorry guys for not updating. Exhaust refit took more time than I thought. I fell into my engine room the day after posting about after having the cockpit floor removed. Knocked myself out and dislocated a shoulder in the process. (yes, idiot - i know i know...)

Have finished refit BUT - there is a problem with the fiberglass bends I had made. They seem to have melted and collapsed in on themselves at the seam where the clamps are. We were able to fix the gaps caused by the bending with epoxy and use a thinner clamps on the fiberglass/silicone joines. I believe the original clamps (around 1 inch wide) didn;t 'pinch' the soft silicone hose to the fiberglass until too much pressure was used causing deformity. I shall be off to the fiberglasser to chat to him about the issue next week hopefully.

Until then - I've been trying to flush out/clean up an engine that had salt water ingestion due to a failed raw water pump seal. Didn;t notice it until end of a 50mile transit (luckily done at 7kn not 14) when I did a quick visual of engine prior to shutdown. Engine didn;t miss a beat all trip - temps and oil pressure constant as was rpm. Obviously this is a higher priority than the exhaust (which is now working fine).

Sorry I will post pics soon as I know this exhaust refit may be of interest to others.

I get worn out saying the same thing, but for future reference problems like this best go to the internet site boatdiesel.com. Especially for those with common high speed diesels and high temperature exhaust runs like found on a Riviera. This forum is fun and populated with many very nice and bright folks. Some of whom indeed are experts regularly posting on boatdiesel.

My read of this thread is a fire at sea was a possibility due to an unconventional attempt at redesigning an exhaust run. BTW, I've been on two different models of the Riviera 35. My recollection is a lot of good thought and planning went into the design of these vessels. A query back to the builder and the Riviera forum may well have provided a good answer as to how to replace and upgrade the exhaust systems.

Sorry for the rant, but some of this stuff can get serious, even dangerous.

RAnt away. I've got time.

The exhausts were never 'hot' - we had only tested under idle and displacement speed. They were always only warm to the touch - both the exhaust pipe and exhaust elbow. I said they 'seemed' to have heat-deformed - but that is not confirmed yet. I've yet to speak with the fiberglasser, but I know he used heat-proof epoxy. Once fixed with smaller clamps (not as much pressure) everything was fine for 7 hours on both motors and another 7 home on the starboard.

No excess heat in the pipes or engine, no strange fumes underway or on arrival and all seems to work fine. Fiberglass and silicone is hardly 'experimental' engineering with regards to exhaust systems. I did not alter any of the design of the exhaust other than the materials used.

Oh, I'm a member of boatdiesel.com as well. There is no riviera forum. I planned my new system exactly by reading around and checking forums etc for ideas of how others have done it. So rant away if it makes you feel better. But before you cast aspersions on my mechanical abilities and research practices, please post your qualifications that give you the right to belittle me based on 'your read' of the situation.

With respect.

shufti said:

RAnt away. I've got time.

Oh, I'm a member of boatdiesel.com as well. There is no riviera forum. I planned my new system exactly by reading around and checking forums etc for ideas of how others have done it. So rant away if it makes you feel better. But before you cast aspersions on my mechanical abilities and research practices, please post your qualifications that give you the right to belittle me based on 'your read' of the situation.

With respect.

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I guess that bump on the head made you a little overly sensitive.

I'd say your fiberglass guy F-ed up. With the proper resin and glass lay up those elbows should have never collapsed in on themselves. Wider clamps should not be a issue.

I'm wondering that myself, Capt Bill (re: not correct fibreglass resin).

Bump on my head is well fixed. But I have been in a engine room all day running motors and changing oil. I'll freely admit I'm not in my most sociable of moods. Sorry, but sunchasers post did rub me the wrong way. He was so concerned with what was being spoken about here but he did notihng until after the fact when all he could offer is a 'didn't think it would work'.

I am also a member of Boat Diesel. Great go to site but not one that I like to browse of an evening. Trawler Forum is. Many people post their questions on multiple sites and post the results here, which is great and much appreciated. If everyone posted Garmin problems on Garmin's site, Fiberglass projects on Boat Builders.com etc. we wouldn't have to much to talk about here.

shufti said:

Hi All,

The stainless exhaust pipe from the riser to the muffler has developed some rust and pinholes have started to occur. I'm considering switching to a flexible hose product rather than having new stainless pipe fabricated.

Can anyone offer any advice on doing this? Seems all the flexible pipe available is only rated to +100C and I assume temps would be higher than this as the pipe is situated just aft of the turbo. The motor is a Volvo TAMD41A.

Just started my search today so any and all advice/warnings etc are welcome.

Thanks.

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Shufti, I was pretty gentle. I'll keep it simple.

You elected to go away from engine/ boat builder's specs and materials to save by your numbers $200 or so. At low speeds and presumably very low EGTs your revised system "melted" (your word). If part number 24 and clamps show heat related problems, is part number 20 (exhaust elbow) suspect?

What did your IR gun show for temperatures around the exhaust system on your cruise?

Sunchaser and other members,

Firsly I do apologise - I was in a pretty shitty mood. Your post did rub me the wrong way for a few reasons. I didn't just jump into this modification without (what I consider) due diligence. I have not modified the system in any way, other than materials used. The new materials I've used are not experimental - they are tried and tested. Whilst my third post makes it seem so (bad wording on my part) - the primary reason for going the way I did was not just to save a few bucks. Save some dollars and end up with a better system - sure. If I had any doubts the fiberglass would work I would not have even entertained the idea.

So can we talk this through because I am genuinely interested in fixing it properly. I never did an IR thermomter reading on the pipes becasue they were only warm to the touch. Not hot. Original injection elbow - part 20 - included. The elbows are not in new condition, but they are certainly still serviceable and far from needing replacement. The 7 hour cruise was done at same (displacement) speed as the test. 2100rpm (as opposed to 3600 cruise rpm) - so the motor was not working any harder then during testing.

No more deformations occurred once we changed the clamps (just prior to the 7 hour cruise).

The deformations were specifically local to the clamps. There was no deformation in 'unloaded' sections.

As I said - I will be removing the bad sections and taking to the glasser this coming week. I'd have done so sooner but the engine situation obviously has taken precedence. I needed the exhaust together and working to be able to run the engine.

Shifting

No apologies necessary. Keep us posted on how it all works out.