hump hose moves - why?

[Randy and Mary Davison]

I was working on the raw water pump today and happened to grab the hump hose.  It moved about 1/16th inch at the top and appears to be pivoting at the engine exhaust flange and is definitely loose.  The nuts on the flange are tight.  After searching and reviewing postings in the usual places, I can't picture how it can be loose without loss of coolent.  There is some powdery carbon deposited on the heat exchanger upper surface.  I can't build a mental picture of what's going on as I don't have a diagram of how that assembly goes together. 

I sprayed penetrating oil on the exhaust flange nuts and will pull it apart tomorrow.  Meanwhile, any info you can give me will be very helpful.

Can't remember if my signiture has full info so:  M35A, Hull number 1268.

Thanks

Randy

[Stu Jackson]

For Mk Is, here's a Catalina Yachts drawing.  The hump hose is item #6 in the drawing.

[Randy and Mary Davison]

Thanks Stu.

I have a terminology problem I think.  Everything is solid at the muffler end.  The motion I'm seeing is at the engine end when I grab the insulated section and wiggle it back and forth.  Based on reading earlier threads, it looks like the last section screws into the exhaust flange and may have failed there.  I don't see how it can wiggle otherwise but it is limited in travel so can't just be broken off??

Hopefully the flange will come loose easily and I'll be able to see what's happening. 

Randy

[Ed Shankle]

Sounds like you are actually referring to the exhaust riser and that the seal between the flange and the riser has been lost. After you uncouple the flange from the manifold, you can reseal with the proper pipe cement.

Ed

[Stu Jackson]

Here's a link to a gasket discussion:  http://c34.org/bbs/index.php?topic=1892.0

A friend recently fried his exhaust riser and I gave him a bunch of information for replacement.  See the Knowledgebase, under engine, and there are very good descriptions written by Ron Hill and others about the system shown in the drawing above.

[Ron Hill]

Randy : I believe that you grabbed ahold of the "exhaust riser" and it was that stainless pipe that moved.  Stu's drawing is from the very early 1986/87 black iron pipe screwed together riser.
If something moved you have a loose flange and or a rotted out stainless riser pipe at the flange.  Best better do some checking. 
The factory will make you a new stainless riser - might have to send them the old one!   

[Randy and Mary Davison]

Thanks all.  Ed was right on.  The riser threads lost seal in the engine flange allowing the small movement.  It's all back together now with hi temp thread goo and will be tested when I complete all the rest of the maintenance.  I plan to write up my experiences as an exhaust first timer to add a bit to the body of knowledge in existence.

Stu, I had found and printed out all the materials on all the sites.  The problem I had was that the definitions of the parts wasn't quite clear to me.  Was the "riser" the exhaust pipe or only part of it?  Why is the hump hose called a hump hose?  The only "hump" I have in my system is the shape of the whole exhaust pipe (riser).  My hump hose as intalled by Catalina is just a length of exhaust hose - nothing hump about it!  As is the case in so many of these things, once I worked through it, it all became obvious!

By the way, the new index is fantastic!  I found an article that I'd missed in previous searches.

After working on this exhaust system for three long days (including some raw water pump issues et al), I now know that my Karma is, in fact, 0. 

[Stu Jackson]

Nomenclature (too late to help Randy, who now knows it, but to parallel the picture I posted above)

From the manifold towards the muffler:

gasket
flange
exhaust riser - many tech notes and my Feb 2004 Mainsheet Tech Notes (http://www.c34.org/mainsheet/pdf/Feb_2004.pdf) hads a picture of it before installation
water injection nipple
hose to the muffler -- this hose was originally made of hard black reinforced wire hose which tended to wreck the muffler lip it was connected to; the Trident hump hose, noted in many tech notes and on this MB, was especially developed to replace this inflexible hose and reduce the vibration.

[Ron Hill]

Randy : You need to get the terms correct!! 
1. At the exhaust of the engine there is a metal "flange" that attaches with 3 bolts to the engine.
2. Into the aft of the flange is screwed in a "exhaust riser" (stainless pipe).  It goes aft about 5 inches, turns to port about 12 inches and then turns down.  It has a welded nipple for the HX output water coming from a vented loop valve.
3.  The end of the stainless riser is connected to the intake of the aqualift muffler with a hose.  The old hose was a ridged black wire reinforced hose, the NEW MKII hose is a blue "hump hose" with a bulge in the center of the hose.  Most of us Mk I owners have purchased a new hump hose from Catalina parts.  It takes up the vertical vibration of the engine and saves the molded fiberglass intake on the muffler. 

There are a few pictures in the Mainsheet tech notes on the hump hoses - mine and Stu's. 

[Randy and Mary Davison]

Thanks Ron.  You probably won't see this for while now that you're cruising but all is working fine now.  There was no apparent impact from exhaust leaking by the threads in the flange so I gooped it up with exhaust sealer and put it back together.  I've also ordered the silicon hump hose to replace the wire reinforced one.

Randy

[Stu Jackson]

Randy

What exhaust sealer specifically did you use?

[Randy and Mary Davison]

Stu, 

Name slips me.  I'll look next time I get to the boat in a few days.  I asked my local diesel mechanic/parts supplier what their guys use for repairs and bought a tube.  It's about the messiest black goo I've ever used but remained soft and malleable for the whole time I screwed and unscrewed the flange trying to get it to fit right.  Then it hardened up perfectly when the riser and flange heated up.

Randy

[Kyle Ewing]

Randy,

I'm also interested in the pipe thread sealant you used.  I had the same problem (slight exhaust leak around the threads) and a very slight movement of the pipe in the threads.  My stainless riser was in good shape, no corrosion thanks to the fresh water I sail in.  I cleaned everything and reassembled with sealant and it was fine for a short while.  The stuff I used dried hard so it either cracked or I didn't use enough because leak is back and I still have some play.

By the way, wear a dusk mask if you remove the insulation around the riser to inspect.  There was a lot of very fine fiberglass dust when I took mine off.

Kyle Ewing
Donnybrook #1010
Belmont Harbor, Chicago

[Stu Jackson]

I just bought some High Temperature RTV today, it's a SEALANT, not muffler paste.

Kyle, the corrosion isn't from the seawater alone, it's more from the mixing of the hot exhaust gases with the cooler water.  Don't mislead yourself that your issue in fresh water is much different: they tend to rot from the inside out!  The weakest link is (usually - see below) at the exhaust riser nipple where the "raw" water comes in.

We had about 1,376 engine hours when ours went, completely and catastrophically.  #635 did hers in less.  Dave Davis suggested an engine hour log of when they failed (not IF!) a few years ago but we didn't keep track. 

Last year a member reported his experiences and you can do a search on exhaust risers and find his story, and his engine hours. (http://c34.org/bbs/index.php?topic=2372.0) Some fail at the flange, too.

For those of you with exhaust risers that haven't been changed and your engine hours exceed 1,000, don't say we didn't warn you.

[Randy and Mary Davison]

Stu and others - haven't been back to the boat yet so no name yet but it was a sealant - not muffler paste.

Randy