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Old 09-24-2020, 04:33 PM   #1
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Exhaust Hose Replacement on Mainship 400 Trawler

I have a 2005 Mainship 400 Trawler and I want to replace the exhaust hoses as a preventative measure given their age. The one that baffles me is the large hose that leaves the muffler and goes out of the boat at the waterline on the starboard side near the stern. The boat is in the yard a couple of hours away from me, so I had to borrow KapnKarl’s photo and mark it up. See the arrows I drew on the photo - it’s that hose that is troubling me.

Has anyone tackled this job? Even the yard guys are scratching their heads, and if some has done it, perhaps I can pass along a few tips.

There is no room to remove the muffler - look at the spot I circled - no room to tip it. We think it was dropped in during construction before the deck and house was dropped on. I really don’t want to cut the cockpit deck to get at this.

Is it possible to unscrew the muffler from the floor, assuming there aren’t screws on the inaccessible side, and then slide it forward to to get the hose off?
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Old 09-24-2020, 04:52 PM   #2
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That certainly was nice of Mainship to install it like that wasnít it? How big a diameter is the hose in question? You are going to have to think outside the box on this one. Can you fit a dremel tool with the extension on it to maybe grind off the head of any hard to access screws.
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Old 09-24-2020, 05:35 PM   #3
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That hose has never seen more than 100 degree's F in 15 years. I would be more concerned about the clamps than the hose itself. In some boats owners have cut hatches in the deck for access. Some yards employ small people for these type jobs.
If it's out of the water take a look at the inside from the outside. Any signs of delamination will be evident on the inside, and that run looks very short.
I doubt the muffler is only screwed down on the accessible side, it was installed with the deck off and they would have seen a hole for a screw and had to screw it down.

If boat repairs were easy, there would be no challenge

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Old 09-24-2020, 06:57 PM   #4
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Any possibility of removing the muffler screws and just spin it to disconnect and reconnect everything?


Sounds goofy but I have done goofier.....
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Old 09-24-2020, 06:58 PM   #5
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I replaced the hoses from my elbows to the inlet side of the mufflers a year or so ago, it was a difficult job, one of the worst I have ever done on the boat. But I have a twin and by far the worst side was the port side as it is hidden behind the genset. Looks like you have a single, so much easier access. Stb side went pretty quickly.



I looked at the hoses from the muffler to the exhaust and decided not replace them. As Keys Disease said, it is a very short run that doesn't get a lot of heat. You can stick a flashlight and a mirror in from the outside and examine the inside of the hose, or maybe use a endoscope. If you aren't seeing bubbling on the outside of the hose or the wire rusting and popping up through the outside layer (that's what my hoses were doing and they still weren't leaking) I wouldn't mess with it. Certainly not if it means cutting holes in the boat.


But, it may be best to wait and see what some of the many guys on here who are much better mechanics than me think. They might see it differently.
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Old 09-25-2020, 11:28 AM   #6
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Part of why I want to replace this hose is that there is something up with the vent hose where it is connected to the fresh water tank and to get at that, I have to pull the exhaust hose. So long as I’m paying for labor to take it out to get at the water tank vent hose, I’m not putting a 15 year old hose back in. So, that’s part of my motive to fix something that ain’t broke...because something behind it is broke.

Anyway....another idea to float...does anyone know why the muffler on these boats (mine is a single Yanmar 370 hp engine) is so large in the first place? I am wondering if it would be possible to cut the muffler up to remove it and replace it with a smaller Centex/Vernalift, or something similar. The mufflers on my 550hp Detroits (8v92TI) were smaller than what’s on this little Mainship. That’s why I don’t understand why these have to be so big.

My partner is going to call a muffler expert identified on Boat Diesel and see what gives, but if someone has already done this, then why reinvent the wheel.
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Old 09-25-2020, 12:12 PM   #7
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Hard to see what all the options may be from your picture but cutting the fiberglass exhaust tube and glassing back together should be an easy task for a glass guy. If needed the tube could be cut right out of the muffler and a new tube glassed in. I don't think they use much magical stuff at the factory to put the mufflers together other than use fire retardant epoxy.
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Old 09-25-2020, 12:29 PM   #8
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Hard to see what all the options may be from your picture but cutting the fiberglass exhaust tube and glassing back together should be an easy task for a glass guy. If needed the tube could be cut right out of the muffler and a new tube glassed in. I don't think they use much magical stuff at the factory to put the mufflers together other than use fire retardant epoxy.
Good idea. Let me run that up the flagpole! Thanks.
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Old 09-25-2020, 02:05 PM   #9
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Mermaid, take a look at this site. I came across it while designing a new exhaust system for my Allied Seawind. Looks like they build/modify components in place.

https://www.sbmar.com/articles/build...xhaust-system/
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Old 09-25-2020, 02:22 PM   #10
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Thanks, Duvie. We had already come across that and that is exactly who we are going to call about whether it’s feasible to re-do the muffler into something that is better suited for the space we have so we can maintain other components behind it.
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Old 09-25-2020, 03:55 PM   #11
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What you have is a simple lift muffler. There is nothing inside: the inlet pipe comes into the unit and the outlet starts somewhere between near the bottom and half way up and comes out. The drain in the photo is to reduce the chances of backflooding because the entire system is so close to or below the waterline.

Typically the larger the muffler, the quieter it will be. Yes you can replace with a Centek or similar silencer that is smaller, expect it to probably be louder

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Old 09-25-2020, 04:34 PM   #12
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If the exhaust system has never overheated due to loss of cooling water and the hoses all look good and feel good and you can see the entire run, then the hoses are still ok.

I have not replaced any exhaust hoses yet, I have had the risers off and when looking inside they all look ok. I have had the mufflers off and the rubber joints to black plastic pipe also look great, and I bet these are decades old, boat is from 1970.

The hoses closest to the exhaust riser will get the most wear.
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Old 09-25-2020, 06:13 PM   #13
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I don't think they use much magical stuff at the factory to put the mufflers together other than use fire retardant epoxy.
I doubt its epoxy
More likely vinylester which most of the off the shelf water lifts use.
Takes a higher temp than epoxy and cheaper than as well.
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Old 10-01-2020, 10:17 AM   #14
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I went to the yard yesterday and had the opportunity to inspect the inside of that hose from peeking in through the exhaust tube coming out the side of the boat. The hose has to be replaced. There is rust showing through where the reinforcement wires are. And it has an ever so slow drip inside - something I noticed before I got to the yard. At present, the plan is to disconnect the hose coming into the muffler, shove the smallest yard guy they have into the space in front of it (kicking and screaming, if necessary LOL) so he can unscrew the muffler from the floor on the side we can’t reach. Then, they will slide the muffler forward to gain some access to repair the water tank vent line while the exhaust hose is out.

I’ve asked them if they want to use the silicone exhaust hose, assuming it’s even appropriate in that spot, because it may be more flexible and easier to re-install.

It will be a very busy next 30 days for the boat. Sandblasting of the hull starts today. Looking to add a stern thruster while she’s out, too.
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Old 10-01-2020, 05:31 PM   #15
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Curious what yard you are hauled at? As you're a local are you somewhere you have good experience?

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Old 10-01-2020, 06:06 PM   #16
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Curious what yard you are hauled at? As you're a local are you somewhere you have good experience?

I’m not exactly local. It takes my whole day to go to the yard, check out the boat, and drive back home. The boat is in Stuart, FL and I live just south of downtown Miami. She’s at River Forest Yachting Center, hauled out for the hurricane season. It’s a first time experience with this yard, but I’ve heard nothing but wonderful things about this years across various forums, and word of mouth on my dock in Miami from others who go there. The yards in Miami leave a LOT to be desired in terms of honesty and fairness. There is no yard in Miami I wanted to go to for work on this boat.

My plan is to haul out there every year for hurricane season and get my yard work done while she’s out. I just bought the boat at the end of February, and by the time I got her home in March, COVID had hit, and there she sat in my slip until I left in August to go into storage. I’m getting work done that really needs to be done that I can’t do in the water, and which will get the boat to what I want her to be. Next year should be simple. A lot of what I’m doing now is milestone work. Boat is 15 years old and it’s time to replace some original stuff.
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Old 10-11-2020, 10:57 AM   #17
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Exhaust Hose Replacement on Mainship 400 Trawler

Quote:
Originally Posted by Mermaid View Post
I have a 2005 Mainship 400 Trawler and I want to replace the exhaust hoses as a preventative measure given their age. The one that baffles me is the large hose that leaves the muffler and goes out of the boat at the waterline on the starboard side near the stern. The boat is in the yard a couple of hours away from me, so I had to borrow KapnKarlís photo and mark it up. See the arrows I drew on the photo - itís that hose that is troubling me.

Has anyone tackled this job? Even the yard guys are scratching their heads, and if some has done it, perhaps I can pass along a few tips.

There is no room to remove the muffler - look at the spot I circled - no room to tip it. We think it was dropped in during construction before the deck and house was dropped on. I really donít want to cut the cockpit deck to get at this.

Is it possible to unscrew the muffler from the floor, assuming there arenít screws on the inaccessible side, and then slide it forward to to get the hose off?

Reading your post with interest. I have an older MS and will be inspecting the exhaust hose before I launch.

Please post back what the yard actually did to replace the hose between the muffler and the hull.
You asked if the exhaust outlet is in or out of the water. Mine is partially submerged by maybe 1".



BTW I have my boat at Indiantown Marina. About 1.5 hours further west up the St Lucie canal. IMO they are much better protected because of the mid-state location.
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Old 10-11-2020, 11:00 AM   #18
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Stern Thruster

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Originally Posted by Mermaid View Post
I went to the yard yesterday and had the opportunity to inspect the inside of that hose from peeking in through the exhaust tube coming out the side of the boat. The hose has to be replaced. There is rust showing through where the reinforcement wires are. And it has an ever so slow drip inside - something I noticed before I got to the yard. At present, the plan is to disconnect the hose coming into the muffler, shove the smallest yard guy they have into the space in front of it (kicking and screaming, if necessary LOL) so he can unscrew the muffler from the floor on the side we canít reach. Then, they will slide the muffler forward to gain some access to repair the water tank vent line while the exhaust hose is out.

Iíve asked them if they want to use the silicone exhaust hose, assuming itís even appropriate in that spot, because it may be more flexible and easier to re-install.

It will be a very busy next 30 days for the boat. Sandblasting of the hull starts today. Looking to add a stern thruster while sheís out, too.

If you add a stern thruster, please take a few out of water pictures. And who did the install and what thruster you used. My research suggests going with the next bigger thruster than the yard or installer suggests to get better response for not much more cost.
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Old 10-16-2020, 04:48 PM   #19
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I hope to get some photos from the yard. The work is being done now. I’m a couple of hours away from the yard, so I can’t drop in for a visit very easily.

The yard decided the best approach would be to shove their teeny tiniest worker in front of the muffler to reach the screws on the outboard side of it, and after removing all the other screws holding it down, slide it forward to gain access to pulling the hose off.

I went with Side Shift for the stern thruster, external mounting with no holes drilled below the water line, adding a dedicated 24v battery bank with its own charger. Yes, I upsized that to the one that is rated for up to a 70-footer. The new remote is wireless and will also operate the original Side Power bow thruster.

So, while she’s spending some time at the “spa”, she got fitted with a sandblasting skirt and shed a few pounds of old bottom paint. She’s getting barrier coats and new bottom paint now.

I’m tackling a few other things, too, while she’s sitting out hurricane season - hooking up the new head PVC “hoses” I made up, installing a new dinghy lift to get the dinghy off the platform, building a little storage drawer under the dinette seat, new bimini canvas, and more. Can’t wait to get her back in a few weeks.
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