Engine Vibrations & Hump Hose Discussion

[Ken Juul]

One of my winter projects was to replace the engine exhaust hump hose.  I had noticed a slight water leak coming out the bottom that tightening the clamps would not stop.  Visually it looked ok, but as I took it out I realized how hard and brittle it was.  I was concerned about the motor mounts because of vibrations but they were tight and the rubber remains in good shape.  I was amazed during my first trip how much quieter the engine was with the new soft hump hose.  If you haven't converted yet, for about $30 and a half hour of work it is a great upgrade.  

When you think about it, it all makes sense. I should have realized the heat and age stiffened up an all ready stout hose.  Wriggling my hand back there and giving a squeeze rather than just a visual check would discovered the problem earlier.  I'm a bit surprise that it didn't cause an exhaust riser problem.

[karista]

Ken
Just yesterday, I too noticed a black buildup at the bottom end of the original hump hose, exactly as you described. I had previously ordered the new style hump hose from Catalina. Did you have to remove the manifold to install the new hump hose or did it flex enough to install it w/o removing the manifold?

[Stu Jackson]

Did you have to remove the manifold to install the new hump hose or did it flex enough to install it w/o removing the manifold?

The exhaust riser is SCREWED into the flange at the back of the manifold.  The hump hose connects to the other end of the exhaust riser below the nipple.  Unless you've used concrete to seal the threads (I used muffler patch paste) the riser should be able to move enough to easily install the hump hose.

I've read about folk's difficulty getting the hump hose on, but I have, to date, been unable to understand why the riser shouldn't be able to move.  I am, however, concerned about breaking any "seal" that the muffler patch paste may have made on the threads and thus getting some blowby at the aft end of the manifold where the riser connects, if the riser does indeed move.

[Ken Juul]

Getting the old one off was the hard part.  Used a hacksaw to saw to cut about a 1" piece out of the middle of the hose.  Then felt inside each end to find how much room I had.  Cut off another ~2" off the top half and use big channel locks to twist it off.  There was then enough room to twist/pry the bottom half off.  Getting the new one on was a piece of cake.  Trimmed about an inch off the 8" replacement, sprayed well with silcone spray and slid it up the exhaust pipe as far as it would go.  Then used a long screwdriver to lift/squeeze the bottom end until it popped in place.  Slid the hose down onto the muffler and tightened the clamps.

[Ron Hill]

Ken & All  : You are saying that "your hump hose was hard and brittle"?  or did you mean that the old black solid exhaust hose installed by the factory to the muffler inlet, was hard and brittle?? 

It sounds like you changed to a new hump hose (Trident, light blue and very plyable). 
I first installed a Trident "hump" hose in 1999? and wrote it up in the Mainsheet.  It saves vertical compression/vibration on the muffler inlet subsequent cracking of that flared inlet.  When I change out my engine that hump hose was still very plyable 10 years & 2000hrs  later. 

[Ken Juul]

The old black exhaust hose was hard and brittle.  I did read the article, when I looked at the muffler with the engine running I did not see what appeared to be excessive engine movement.  Thought the engine noise was normal until I changed to the blue hose.  Now I realize the engine was using the muffler as a drum adding to the overall noise level.

[horsemel]

Sometimes I fear to read these posts cause I know it will involve work, money or both.  Put Blue Moon in the water today after rebedding chain plates and running new wire up the mast and replacing mast lights.  Engine started right off.  After getting to the dock I did an inspection to make sure no thru hulls were leaking and packing gland was fine.  Low and behold I noticed the two hoses that come vertically (beneath the head sink) out of the muffler were seeping water at the joint where the hoses meet the muffler in the top of the muffler.  (Is that what you mean by a riser?)  Is this just cause the clamps are loose or do i need to replace the hoses?  I suspect they are original, so will replace them, just was hoping not now.  If so i might as well do the hump hose as well. (What is the exhaust manifold?)  I will remove the aft bulkheads this weekend and look further at the thing.  The square fiberglass thing beneath the head sink is the muffler, that I know.  Questions: Is there a part number for the blue hump hose from Catalina Direct or do I just ask for the blue hump hose?  Can I replace the other hoses with hose from a local source or are these hoses special shaped or some other unique characteristic?  Is there a drawing someplace of the muffler and the hoses? Lastly, can you replace these hoses with the boat in the water or will the boat flood when I take off the hose that goes out of the boat?  As you may have guessed, I did not spend my youth hanging around the auto shop.  Don't know a manifold or a riser from squat.  i usually can figure out your terms with a little description.  She is a 1988 with a 25xp.
Mark Mueller

[horsemel]

I got the blue hump hose figured out.  Catalina Direct has two a 6" and 8".  I think I want the 8" right if I read Ken's post properly.  I also figured out the riser thing cause they had pictures on the same page as the hump hose.  Is the nipple you guys refer to the narrow pipe that angles off of the riser?  I really need to get behind those bulkheads.
Mark Mueller

[SeaFever]

Mark,

The muffler (the black FG thingy your mention) has two hoses connected to it. The IN comes from the engine output, through what is called the exhaust riser. The exhaust riser is the insulated thing connected from the back on the engine to the IN of the muffler. There is a water input going into the exhaust riser that comes from the HE (Heat Exchanger) and connects to this exhaust riser. The second connection on the muffler is usually vertical and that ultimately goes to the exhaust output at the back of the boat.

There are two main hoses in this section of the exhaust system:

1. Going down from the other side of the exhaust riser to the muffler IN. This is where the 'hump hose' that Ron has talked about can go. You need to measure the length of the hose needed so you can order the appropriate hump hose from Catalina direct.
2. Going from the muffler OUT to the boat exhaust. This usually is a long one piece exhaust (could be different in disparate boats)

I would suggest you check which one of these two is leaking for you on the muffler side. It may as well be that the clamps are loose and you can check it my tightening the clamps. It could also be that the input sections (also called nipples) on the FG muffler are damaged and therefore are leaking. If tightening of the clamps does not help you then you have to check the muffler input nipples. To do that you will need to pull out the hoses. As you have gathered, that could be difficult given how old they are and so on. After checking these things you can decide if you want to replace the hose going from Exhaust riser to muffler IN with a blue hump hose. Note the hump hose is not going to help your leak (unless by chance that specific hose on your boat is damaged), it will just help against the engine vibration damaging the muffler input nipples that can happen by using a hard walled hose in place of the soft silicone hump hose. Yes, the hump hose also will help reduce the transmition of the engine vibration to the hull.

I found a schematic that may help you understand the above better. See the attached drawing for C34. Item 5 is the nipple in the exhaust riser. Item 6 called 'flex' is where the hump hose goes. Item 10 is the other hose going from muffler to exhaust.

Hope that helps. Post if you still have questions and the good people on this forum will help.

[Phil Spicer]

Mark, good to hear the chainplate & wire projects went well. Now, follow the last post plus the Wiki no this project & you should be good to go....Was good to meet you & help with the masthead.
Sail safe
         Phil Spicer

[Stu Jackson]

Mark,

www.marinedieseldirect.com should be on your list of bookmarks.  It includes this:  http://www.marinedieseldirect.com/universal/200157/universal-owners-manual-m25xp-specifications.html

The exhaust manifold is the part of the engine that has the removable cap where you put the "antifreeze" into the engine.  That where the exhaust riser connects to the engine.

Spend some time learning about the parts.  Most of us weren't diesel mechanics before we bought our boats either.  Don't feel bad, you're actually way ahead of the game:  you're here and learning.  Think about how snafu'ed some folks could be without this valuable resource, which is  available to anyone with a C34 or other boats with our systems and either don't know about it or ignore it.  They're the dumb ones.  Really dumb!

There's also the Manuals section of this website with blow up drawings of all the parts.  Take 'em one by one!  I get there from the home page, bottom, or via the C34 Tech wiki.  Here: http://www.c34.org/wiki/index.php?title=Manuals

Here's a hump hose installed.  The wrapped insulated pipe is called the exhaust riser and it goes over to connect to the back of the engine.  The hose connecting to it right above the hump hose is the engine water raw water output from the HX.  That's called the nipple.  The exhaust hose is 1 5/8 inch or 1 1/2 inch "exhaust hose" specially made for the very hot gases and water it carries, and it goes from the muffler to the transom.

Catalina Direct?  The website shows this:  http://www.catalinadirect.com/index.cfm?currentpage=2&fuseaction=category.display&category_id=71 There are only two lengths of hump hose.  Only YOU can tell how long it needs to be on your boat, but longer is better ''cuz you can't make a short one longer.  It's part of the "Catalina boats over 30' " section.  Only two they have for our boats.  Glad you found those things on their site.

Exhaust riser picture, in addition to this photo below and Mahendra's excellent sketch.  Here:  http://www.catalinadirect.com/index.cfm?currentpage=1&fuseaction=category.display&category_id=71
 

Actually, it's great that Catalina Direct is making exhaust risers - they were becoming a pain to get from Catalina, who at one time required you to send your old one in 'cuz they got burned by making the wrong ones and getting returns on them.

Many people have expressed concern about leaks at the connection of the hoses to the muffler.  I read about it in the old FAQ section, now part of the wiki.  I have, over the years, had to build up the inlet ports of the muffler with Marine Tex, an epoxy material, to strengthen those tubes at the top of the muffler to which the hoses connect.  Like this:  http://www.c34.org/wiki/index.php?title=Muffler_Replacement_or_Repair

I don't understand your reference to the aft bulkhead removal.  All this stuff is under the head sink and in the engine compartment.

All this stuff can be done with the boat in the water.  The exhaust hose is available at local chandleries.  You may have to special order the 17+ foot hose from the muffler to the transom because I've learned that standard lengths are only 12 feet.

Basically, all this stuff is either of two things:  you have a mechanic do it, or you consider it a safety issue, learn about and either work on it yourself or still have the mechanic do it.  Your boat, your choice.  I prefer doing it myself, because the few times I've had other people work on my boat they've messed it up so I have to do it myself anyway.  It takes longer, but I find it costs less in the long run.  Plus, I always learn something new.

[karista]

Mark
I just finished installing a new Hump  hose yesterday. I had discovered a black leak at the bottom of the muffler connection as Ken described above. I first tried to tighten the clamps, but this did not help. Removing the original black hose took me a several hours, it was rigid and seized on to its connections. I used a sharp knife to cut it in the center and then used a dremel tool to slowly cut each wire which is embedded in the hose. I did not want to use too much force to break its seal at the muffler as it could easily break the epoxied nipple causing much bigger problems.After cutting each wire I used a sharp knife to cut each end of the hose and removed it. Installing the new 8" Hump hose required shortening it by 1" otherwise it will not go on w/o removing the heat riser which is rigidly attached to the manifold and has NO flex. Based on the condition of my original hump hose which was hard as a rock I strongly recommend to replace it. It is not a job you would want to do at sea, but doable at the dock in the water.

[Ken Juul]

I did the entire process from the head.  Step one is to remove the access door to under the sink.  Just remove the 4 little hinge screws and door leaving the frame in place.  Using Stu's picture for reference.  Disconnect the water lines to the head sink.  I found just undoing the clamps and pulling the clear hose off the white fittings the easiest.  Before you do, mark one of the lines and fittings so they go back together correctly and don't forget to turn off the fresh water pump

In the back of my head I expected to find the damage to my muffler that Stu described, so I wasn't too worried about applying too much force.  As I said in a post above, I used a hacksaw, standard size, to cut the old black hose.  Makes easy work of the rubber and a few extra strokes to get through the wire.  The old black hose will not be flexable.  The only way to make enough room to get it off is to cut out the center 1/3rd of the hose so you have enough room to work the ends off the exhaust pipe(nipple) and the muffler.  Whole project took about 30 minutes.

I got my hump hose from Catalina Parts.  It was a few $$ cheaper than Catalina Direct, and I needed a couple of other OEM only parts.  Dani initially wanted to sell me the short 6"(?) hose.  When I said I wanted the 8", she conferred with someone and came back agreeing that it was correct for my MK 1.5, but that I would need to shorten it.   So measure before you order.

[Stu Jackson]

And when you install the new hump hose, put Rector's Pipe Dope on the exhaust riser and the muffler.  It helps to seal the connection and also allows you to remove it in the future without going through all the nonsense just described.  One day you'll have to, like, to replace your exhaust riser!

...otherwise it will not go on w/o removing the heat riser which is rigidly attached to the manifold and has NO flex.

One of the reasons your exhaust riser didn't move is the stiff hose that connects to the nipple.  I replaced mine when I was in there.  IIRC it's a 5/8 inch hose.  In my Reply #2 above, I noted how the riser is connected to the manifold, at the flange.  It is "rigidly attached" but there is a thread at the end of the riser which screws into the flange which in turn gets mounted onto three studs onto the aft end of the manifold.  It should be "flexible" and should be able to move (up & down) at the end under the head sink, inherently because of how it IS attached.  I used muffler patch paste on those threads.

[Ron Hill]

Mark : Look at the picture of my installation that Stu posted.  
The smaller 5/8" hose to the right comes off the welded "nipple" is attaches to the vented loop.  It's best to use nylon reinforced hose rather than the more expensive wire reinforced hose (more flexability and less vibration to the nipple weld).  
Also note that I placed some leather as a cushion under the hose clamps.  The blue silicone rubber is soft and I didn't want the hose clamps to cut into it.
Definitely get the longer hump hose - as every C34 is NOT the same.  You can always cut off but you can't stretch!!
The exhaust hose is 1 5/8"ID.  The head hose is 1 1/2"ID 
As many times as I've been in that "under the sink" compartment, what I do is just tape the door so it stays open.

A few thoughts