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Old 09-01-2015, 02:56 PM   #1
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No such thing as 7" exhaust hose

I am finally getting around to replacing the first 6ft of each exhaust hose as it comes off the exhaust riser. The riser is 7" diameter. No big deal eh? undo the clamp, saw off the existing hose at 6ft then couple in the new hose and attach to riser. What could be easier? I should have known better, literally NOTHING on a boat is EVER easy or simple.

I have spent hours searching for 7" ID hose of any kind and have come to the conclusion it does not exist. Seems impossible and even those that sell hose for a living are surprised it is not available. I did find that Parker will make it on special order if you buy 100ft. Obviously no hose, no hose couplers either.

Surely I cant be alone, the boat is not that old and I would think every Taiwan trawler with the same Cat engines would have the same exhaust hose.

Anybody have any idea where I can find the hose or a creative work-around to replace these pieces?? Replacing all the hose with fglass tubing is not an option in my case. All suggestions profoundly and gratefully welcomed, I seem to be at an impasse.
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Old 09-01-2015, 02:59 PM   #2
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Wet Exhaust Hose - Very High Temp - Blue Silicone - Trident Marine - Hose, Tubing & Fittings - Exhaust - Engine Systems - Downwind Marine
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Old 09-01-2015, 03:55 PM   #3
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What engines do you have?
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Old 09-01-2015, 05:00 PM   #4
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Cpt Bill, I have the 3208's

Oliver, the link provided only lists 4, 6, 8, 10 inch diameters. As it turns out you were right anyway, I just now got off the phone with Trident and they do have 7" dia hose but only in the blue silicone. For the 12 ft I need its going to run $2,600.00 CDN or approx $2,000.00 USD "It's insanely priced" at $162.00 / ft.

I don't know if I can bring myself to waste nearly 3K on a crummy piece of hose, I pray the wife doesn't find out.

Still open to ideas / alternatives.
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Old 09-01-2015, 05:32 PM   #5
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That's the best kind of hose to use. Have you tried one of the marine exhaust specialists like D'Angelo in Ft Lauderdale or MES in Alabama?
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Old 09-01-2015, 05:39 PM   #6
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What's the OD on the 7" hose. I have seen this done, but am not endorsing it. If you take a foot of the 7" hose, cut it in half so you have two 6" collars. Put one collar on the exhaust riser and one on the exhaust pipe. Then put an 8" hose in place of the old 7". I would then lock it in place with 2 to 4 "T" bolt clamps on each end. There is very little pressure on the system, so the hose isn't likely to move. It's more about making the connections vapor and water tight. This is not how I do things, but have never been in this situation either. I've seen this on bay work boats where they pull an engine with a 6" exhaust and replace it with a 5" exhaust. I have also seen them take 6" exhaust hose and clamp it down on a 5" exhaust elbow with "T" bolt clamps. Pointless to argue with a waterman's success.

I know I'm going to hear about this, oh well.

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Old 09-01-2015, 05:41 PM   #7
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By the way, MESA sells the Trident blue for $1406 US for 12 feet.
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Old 09-01-2015, 06:03 PM   #8
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Take a piece of 6" FG pipe and wrap glass and resin on it to build it up a half inch thicker than original. Then re use some of your old 7" hose to make a sleeve joint. Use 6" hose to get where you are going and if necessary, repeat and step back up to 7".
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Old 09-01-2015, 08:47 PM   #9
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Oliver was on the right track. Trident Blue Silicone hose is available in 7". You can order six foot lengths of it from a Trident dealer and Trident will drop ship it to you. It's EXPENSIVE! It is very good hose. I doubt dealers stock the 7" as it is pretty unusual. Most dealers only stock the blue silicone in 3' lengths anyway. http://tridentmarine.com/wp-content/...tion-Sheet.pdf
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Old 09-01-2015, 09:25 PM   #10
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The hose can't be just any blue silicone exhaust hose for a run like that. It's going to have to be reinforced. Some blue silicone exhaust hose is not very stiff and could collapse on itself over a long run.

It's really overkill for what you are doing. I'd adapt 8" regular exhaust to your system.

Do you have mufflers? If so, do they have 7" inlets/outlets as well?

Have you talked to CAT to see if they have a riser with a different O.D. outlet?
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Old 09-01-2015, 09:34 PM   #11
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Looks to me like the Trident path is the best way to go. The only other thing I would suggest is a call to CAT. They may know of an option.
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Old 09-01-2015, 10:06 PM   #12
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Bill has a good point. Silicone hose is usually used to make short straight connections. You should check with Trident before you order the Silicone hose.
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Old 09-02-2015, 08:51 PM   #13
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Hmm. My cats use 6" hose. I am glad as it was easy to find
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Old 09-02-2015, 10:00 PM   #14
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Maybe 7" hose is not needed. With appropriate reducers 6" may be just fine - cheaper and easier to install. Suggest you contact Tony Athens.
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Old 09-03-2015, 08:06 AM   #15
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Quote:
Originally Posted by Ski in NC View Post
Take a piece of 6" FG pipe and wrap glass and resin on it to build it up a half inch thicker than original. Then re use some of your old 7" hose to make a sleeve joint. Use 6" hose to get where you are going and if necessary, repeat and step back up to 7".
That would be my choice. Elegant, inexpensive and sound engineering. You could even use short pieces of Trident blue hose instead of the old stuff (if available).

I second a call to DeAngelo in Ft.L for advice. I have found them very helpful, even when its clear I am not a cash customer.
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Old 09-03-2015, 08:21 AM   #16
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Not to question your skills at measuring but having worked around pipe, tube, hose, and round hollow things that carry stuff inside them...How did you determine the diameter with the hose on ? Are you dealing with an inside or outside diameter. If the INSIDE diameter of the exhaust pipe is 7" then you must add the wall thickness to that (x 2) to determine the INSIDE diameter needed to go over it. It is often easier to take the existing hose's outside Circumference then do the math. Just to double check.
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Old 09-03-2015, 08:38 AM   #17
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Personally I don't like the idea of reducing the size of the exhaust as a solution, given issues with exhaust back pressure. I second the recommendation of double checking the OD of the fitting involved. And I especially re-emphasize getting a professional involved. This is a system that affects a very expensive and critical piece of machinery, the main engine, and involves very high temperatures capable of setting the boat on fire. It is no time for amateur hour, or even "semi-pro" hour.
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Old 09-03-2015, 09:00 AM   #18
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As George noted, i wouldn't reduce the exhaust hose size without a long talk with someone at CAT. But going up to 8" shouldn't be a problem.

You most likely could just take short pieces of 6" silicone hose and stretch them over the 7" nipple to make a spacer. One spacer might be enough.

I find it strange that CAT would use an odd sized riser. Was it made by the builder? And could the hose be metric?

Are your other exhaust hose connections down stream 7" as well?
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Old 09-03-2015, 10:07 AM   #19
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Post 13 uses 6 " as do some other 3208 users, depends on vessel exhaust setup and HP. Again suggest talking to a pro such as Tony Athens who has been through this many times.

As an aside to the OP, are your mixing elbows in good shape? They don't last forever.
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Old 09-03-2015, 11:00 AM   #20
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7x25.4 comes pretty close to 180mm. Probably metric. Exhaust mixer usually supplied by boatbuilder, not Cat.

Not a great idea to cut up exhaust stuff until new stuff is on hand.

What was wrong with the old hose?
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