A25 Deluxe, MD3B, Exhaust Question

[stxray]

When I started my MD3B engine, I had water & exhaust spewing from a cracked and broken exhaust hose. Here’s a shot of what the hose looked like when I took it off.

2016-06-15 10.06.47.jpg

Before I installed a new hose, I checked out the interior of the riser pipe and it appears to be in very good shape. The interior wall has no flaking or thinning and appear to be quite solid.
I also took the opportunity to check out the muffler and the section of hose that connects the muffler to the exhaust thru-hull. Both appear to be in good condition showing no signs of deterioration or cracking.
When I removed the section of pipe that connects the riser to the muffler, it was simply inserted into the muffler and secured with a single hose clamp. However, the other end of the muffler, has a short sleeve or coupler with one end inserted into the muffler and the other end inserted into the hose that goes to the thru-hull and double clamped. I installed the new hose the same way (see photo below).

2016-06-15 10.03.36.jpg

So, here’s my questions…
1. Which Is correct? Shouldn’t I also have an insert/coupler on the front end? If so, here’s what I’m thinking I need? http://www.defender.com/product3.jsp?pa ... 4&id=57228. Comments please?

2. Also, here’s a shot of where my thru-hull exits the transom. As you can see, it is below the bottom paint line.

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Given that I have yet to have this boat in the water, I can’t tell you if that line is the actual water line. Is this something for which I should be concerned? After reading the post from Kerrye and his near sinking experience (viewtopic.php?f=28&t=9277&hilit=exhaust ) I’m a little nervous to say the least. On the other hand, this exhaust setup has worked for 40 years, so how bad could it be?

Seeking your thoughts, comments & suggestions. All of which will be greatly appreciated.
Ray

[WillieC]

Ray, slip over to the A25/27 section and read "A25 exhaust system" and "First splash, first (almost) sinking". Take the time to follow all the links. Your muffler looks like the one that blew up on Kerry in Denver. Oh, I see you already read the sinking post.
The line you see on the transom looks more like an old bottom paint line. My exhaust almost splits the water line, of course that is dependent on static load and calm sea.
We are all waiting with bated breath to see what Kerry ended up installing. His near sinking is a warning to us all.

[kerrye]

My hoses were attached to the muffler the same way as yours. Metal insert at the outlet end and no insert at the inlet end. Outlet end was somewhat odd in that insert went into the outlet hose and was clamped but the other end of the insert had a short piece of exhaust hose covering it and that went into the outlet of the muffler and was clamped. I had two clamps on the inlet end of the muffler. I haven't been able to figure out why the outlet has an insert but not the inlet. I would at least double clamp the inlet hose.
As mentioned in my other threads, I'm not crazy about the design of the Elastomuffler. Seems to me it would create excessive backpressure. I was kinda hoping someone with more experience with mufflers and backpressure would comment on this. Has anyone actually measured the backpressure with and without the Elastomuffler?

[WillieC]

We've had some pretty good winds on the Canal the last few days and I have been watching the Willie C rock and roll con mucho gusto, gusts to 25 kt. Went out today to assess the damage, how many broken wine glasses, the like. Watching the to and fro bob and wave I surmised the exhaust system pretty much filled with water. When we fired her, it started and I listened for the exhaust which was silent for a second or two, I am guessing pumping all that water out of the exhaust hose and muffler. Sure enough, with a sharp pop she started burbling like normal and all was good. Back pressure, yes. How much? Who knows but certainly within acceptable limits. But there was a distinctive pop when it cleared. At 5000 feet maybe too much as you suspect, Kerry? (Edit: at 5000 feet, would not the back pressure be less, not more than, sea level? Then again, you are thinking that less atmospheric pressure will shut the engine down sooner when encountering any back pressure. Complicated.) That, and an ancient muffler installed improperly. I stopped short of removing a hose at the muffler, which is no small feat, but I am curious if the high point in my exhaust was not enough to stop the siphoning. Big old valve at the transom going in this winter. Rick

[stxray]

After checking out Kerrye's "A25 exhaust system" post and all its links, here's what I think I'll do...

I can order a 12" piece of 1.75 OD stainless steel tubing. Cut a 4" piece and insert it about 2" into the exhaust hose coming from the engine and double clamp it. Then slip a 2" piece of exhaust tube over the other end and insert that into the muffler. I'd like to double clamp the muffler but there doesn't seem to be enough of a collar to accommodate two clamps. Also, all the photo's I've found online show it with only one clamp on each end.

I also removed the aft starboard bunk board revealing the exhaust hose going to the thru-hull.

2016-06-15 09.59.21.jpg

It looks like I can secure the hose higher in the space and gain some elevation in the run.

I'm thinking this should hold me until I get her in the water and see what, if any changes are needed.

Thanks to all for commenting.
Ray

[kerrye]

While you're ordering stuff, if it were me, I'd order enough stuff so that I could make the exhaust hose complete without the Elastomuffler in place. A piece of exhaust hose the same length as the muffler would suffice as it could be connected to the two stainless inserts. I don't know what the predicted lifespan of an Elastomuffler is, but given my experience, having a piece of exhaust hose to swap in place of it is cheap insurance.

[stxray]

Great idea. Items ordered