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.

What engines do you have?

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.

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?

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.

Ted

By the way, MESA sells the Trident blue for $1406 US for 12 feet.

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".

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/uploads/2014/12/202V-Specification-Sheet.pdf

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?

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.

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.

Hmm. My cats use 6" hose. I am glad as it was easy to find

Maybe 7" hose is not needed. With appropriate reducers 6" may be just fine - cheaper and easier to install. Suggest you contact Tony Athens.

Ski in NC said:

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".

Click to expand...

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.

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.

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.

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?

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.

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?

Thanks guys for all the great suggestions & help!!! I too am beginning to question my measurements but the math works out to 7". I measured the circumference of the exhaust flange and it was 23". I also marked and removed a clamp & measured diameter of approx 7 1/2 OD. Why I didn't just measure the circumference of the hose for OD is beyond me.

Does Cat actually make the risers? These are 3208 turbos with all the cooling crap, mine are heavy stainless and appear mint. There are no mufflers, simple system just straight wire wound rubber hose from exhaust risers to back of boat.

I don't think the boat needs 7" hose, although each exhaust run is 26ft so back pressure "may" have been a concern for the builders with the standard 8" being too large to fit in the allotted design space. Probably the real truth is Albin got a deal on the 7" risers because no one else wanted them due to the fact they required a hose size that does not exist. Idiots!

In any case I'm not trying to do anything fancy here, just replace the first 6ft of hose on each header and couple the new piece to the old hose. Had I normal size hose I could have done the job in the time it took to type this. Alas, sigh... i should have known. I think it is important however that I only have the one splice in each exhaust. I liked your idea Ski but the up & down sizing & extra splice makes me uncomfortable, I have first hand knowledge of how incredibly fast a blown exhaust can sink a boat. Ted, also liked your idea but won't work as I am going from pipe to hose, not pipe to pipe.

In any case I may have solved 50% of the problem. I found a supplier of 7"ID hose in the standard black rubber but believe it or not it has to be custom made. Amazingly they are willing to do a run of 12ft. It is very expensive but still only half the cost of the "ridiculously" over-priced silicone stuff. (Note my emphasis on ridiculous)

The problem remaining is now all I need is two simple 7"OD straight couplers. I had hoped to find some stainless/bronze/plastic/any-kind pipe or tube that I could cut to use as couplers but it seems that virtually nothing is made in 7" except black iron. The OD of 6"pvc is 6 5/8 so would likely work but temp rating is too low I think.

Have you contacted Albin? Or Cat? Perhaps I missed it along the way. But the first thing I would do is contact the builder and second the engine manufacturer. I've got to believe you don't have the only Albin with CAT's ever to have this hose.

Parker is another source for your hose maybe.

Custom Made Heavy Duty Marine Softwall Wet Exhaust Hose, Series ES269 | Parker NA

A bet it's expensive though and as you know, measure twice and then again. (23" circumference gives you a diameter of 7.32")

Thanks Larry, called Parker, they will make it if I order 100ft. Would have to re-mortgage my house to pay for it.

B&B, the boat was a custom build by Albin for the PO, as far as I can determine it is the only one however I did find another similar. It is radically different then all other Albins and Albin isn't very helpful. I don't think the risers were made by Cat and I have a sneaky feeling were custom made as well. In any case, who ever is responsible for the odd hose size, Albin or Cat, it is unlikely they have the hose given the major hose manufacturers don't. I really believe Albin's engineers didn't carefully calculate that 7" was required for technical reasons, rather Albin simply used up some oddball stock laying around over there in Tawain.

Capt Kangeroo said:

I really believe Albin's engineers didn't carefully calculate that 7" was required for technical reasons, rather Albin simply used up some oddball stock laying around over there in Tawain.

Click to expand...

You are likely correct.

Capt Kangeroo said:

Thanks Larry, called Parker, they will make it if I order 100ft. Would have to re-mortgage my house to pay for it.

B&B, the boat was a custom build by Albin for the PO, as far as I can determine it is the only one however I did find another similar. It is radically different then all other Albins and Albin isn't very helpful. I don't think the risers were made by Cat and I have a sneaky feeling were custom made as well. In any case, who ever is responsible for the odd hose size, Albin or Cat, it is unlikely they have the hose given the major hose manufacturers don't. I really believe Albin's engineers didn't carefully calculate that 7" was required for technical reasons, rather Albin simply used up some oddball stock laying around over there in Tawain.

Click to expand...

Regardless Albin should have the drawings and specifications still somewhere. Now today it would be digital but many builders can pull out every boat they've built. If the risers aren't CAT, they might be able to tell you what they are. Just a chance.

Capt Kangeroo said:

The problem remaining is now all I need is two simple 7"OD straight couplers. I had hoped to find some stainless/bronze/plastic/any-kind pipe or tube that I could cut to use as couplers but it seems that virtually nothing is made in 7" except black iron. The OD of 6"pvc is 6 5/8 so would likely work but temp rating is too low I think.

Click to expand...

The straight coupler solution is pretty easy. Contact one of the custom marine exhaust shops. They could easily roll them out of stainless steel sheet metal and weld the seam. Heck they may have some 7" OD pipe available. None of the pipe in my new custom exhaust is standard size pipe.

Ted

Suit yourself, but total cost of ownership is much cheaper for the "ridiculously" priced blue stuff, if you plan on keeping the boat for awhile. And if you go to sell it, it's one of those a knowledgable buyer/surveyor may look at and think, hmmm, I wonder what else they cheaped out on here? At the very least, when they see the blue, it sends a strong clue that there is a bias towards quality on the boat.

For a coupler I'd just buy some of this stuff, cut it down to the length needed and take it to the local welder to have some crush rings made.

Broken record I know, but for less than 500 HP 6" ID hose may prove sufficient. At 375 HP you are well below the size limit. Read boatdiesel exhaust system article for a more detailed explanation. Going to 6" may open up some simpler fitting options. Are you 100% positive of hose and fitting measurements?