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
For Mk Is, here's a Catalina Yachts drawing. The hump hose is item #6 in the drawing.
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
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
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.
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! :cry4`
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.
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.
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. :clap
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
Randy
What exhaust sealer specifically did you use?
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
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
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.
Stu and others - haven't been back to the boat yet so no name yet but it was a sealant - not muffler paste.
Randy
Randy : Try the RTV Hi Temp sealant. Just go to any automotive store and they'll sell you some.
Then tell them what you are sealing. If it's the threaded riser into the exhaust flange they'll probably tell you to use muffler paste - as that exhaust is HOT!! After the raw water enters from the nipple and mixes with the exhaust gas - all cools down considerably!
Your boat - you make the choice. :roll:
Hi Ron,
The job's been done for several weeks. Stu asked me earlier in the thread what I'd used. It was a high temperature sealant recommended by my local diesel repair firm - North Harbor Diesel - but my aging memory can't remember the name and haven't been back to the boat yet to look at the tube.
Randy
This is my last - I hope - posting on my project to stop the play in my exhaust riser. the purpose of posting this is for the benefit of future searchers.
After pulling the system apart the first time, I sealed the flange to pipe threaded connection with a product called Acousti-Seal, recommended by my local marine engine repair shop. Put the system back together with the old "non-hump" hose place - all worked and there didn't seem to be any play. Meanwhile, I ordered the blue hump hose from Catalina Direct with the intent of cutting away the old hose and using the flexibility of the new one to avoid pulling the system apart again.
You can guess...as soon as I put any real pressure on the riser it moved a few thousanths again. I pulled the riser assembly back off, thinking my sealant had failed. What I found was that the motion was at the other end of the short threaded pipe that goes from the flange to the stainless portion of the riser. The flange to pipe seal was solid. I had tried to unscrew the pipe section on the first removal but couldn't get it to turn with moderate force. This time a really reefed on it and it came unscrewed. The threads were good so I sealed the riser end of the pipe with Accousti-Seal and put it all together with the new hump hose installed.
It's completely solid now so I'm pretty certain the problem is solved.
I don't know how the pipe could move a bit in it's threads and still be that hard to unscrew. It went back together with no problems such as being out of round. The lesson is to make sure to get that short section unscrewed from under the wrapping and seal it along with the flange end.
Other notes - you can remove the riser without going through the aft cabin although cleaning the manifold flange mating surface is easier from the back. I did it all from the front on the second removal. Total project time for the second removal was 4 hours including cleanup.
The drain plug on the aft end of the manifold would not come out so I opened up the end of the heat exchanger and also used a PAR hand pump to be sure all of the coolant was removed from the manifold so it doesn't run into the engine when the exhaust gasket is removed.
Thanks to all here for suggestions along the way.