Muffler cracks

[ErikN]

Since we bought our boat we've always smelled diesel exhaust in the salon after motoring. While working under the head sink, I took a close look at our muffler. The top and sides are laced with hairline cracks, and it looks like exhaust/water has been seeping through. All of the posts that I have seen describe problems around the inlet and outlet nipples and the corners, not on the solid faces of the muffler (but I could have missed some relevant posts). Also, it looks like a previous owner coated the area around the drain screw with adhesive of some sort. Based on the attached photos, does this look like the muffler can be repaired?
Erik

[Ron Hill]

Erik : Pressurize the muffler and then you (or a muffler shop) can check for leaks!!

A thought

[WTunnessen]

If you have removed the muffler from the boat, one way to pressurize the muffler is to:

1. cut a bicycle inner tube in half. MTB innertube will work better than a road bike tube.

2. Attach to ends of the bicycle innertube to the exhaust flanges. Clamp the innertube down.

3. Using a bicycle pump,  inflate the inner tube and pressurize the muffler tank.

If the innertube stays inflated, that's a good sign. You could also submerge the whole thing and look for bubbles. (just like looking for a flat on a bicycle tire).

But if it does not hold pressure, or bubbles from the cracks, then it might depend on how bad the leaks are. The drain valve area could probably be repaired but I'm not sure how well an external repair over the cracks would hold up.

[WTunnessen]

Also - was the boat ever located in a place where the water in the muffler could have frozen and expanded if it wasn't winterized?

[Jeff Kaplan]

Eric,

I also have an '86 and last fall I put out that the mechanic stated time for a new muffler.  I just had the job done, with new heat riser, all new hoses. Catalina Direct has the replacement. I got the new style, round, much larger than original.  I was told that when I start the engine in a month or so, it's going to take a while to fill and finally discharge water, the new muffler is over 4 gallons. 10 years ago, I might have done this myself, but as I'm in my 70's, time to let the youngsters take over.  Also a good thing that I had a professional look the boat over, needed a new cutlass brg. and T-G he noticed that the bellows on my dripless packing gland had disintegrated. I might not have noticed until my boat sunk. My advice, get a new muffler.

Jeff

[ErikN]

Based on the black water seeping from the cracks, I'm fairly certain the muffler was leaking. The previous owner had the boat in the PNW for twenty years, but I don't know the location before then. There was no hump hose (I'm adding one), so maybe the vibration did the damage. However, there are no visible cracks around the inlet or outlet. It just looks like someone played football with the muffler.

I have no experience with fiberglass repair, so we decided to splurge on the new model from Catalina Direct. It's extremely expensive, but better than exhaust in the boat. The posts on this forum were a big help—we had no problem moving the old and new ones through the door under the sink. Thanks!
Erik

[scgunner]

Erik,

Replacing your muffler with a new unit is probably the best way to solve the problem but also the most expensive as you've already found out. While repairing your old one would have been the least expensive. Even if you're inexperienced working with fiberglass it's not terribly difficult and very forgiving. Even if you screw up your first attempt you can simply grind it off and start again. Also since your boat is fiberglass it's a skill that's bound to come in handy down the road.

If I was doing the repair I'd grind off the gel coat then epoxy on a fresh layer of glass followed by one or two finish coats of epoxy as required. Plus you can add color to the epoxy to get a nice finish.

[Ron Hill]

Erik : I believe that you made a good decision.  You can get to the point that patching and fixing is no longer a reasonable option.

Afterall it has been installed for 37 years!!

A few thoughts

[Noah]

I agree with Ron. Sometimes a cost/benefit analysis dictates new over repair! Especially when you factor in "time and energy" invloved!

[ErikN]

I'm keen to learn how to work with fiberglass, but I didn't want to make this my first attempt. Maybe I will practice on something that doesn't carry a carbon monoxide risk.

[scgunner]

Erik,

Since you replaced the muffler you can always use the old one as a test mule to practice fiber glassing skills on. As your skills improve I think you'll be amazed at what you can fabricate with epoxy, fiber glass, and wood. If you're concerned about CO I'd recommend a CO detector.