Brittle mufflers?

[John F.]

I'm doing a little work on the starboard exhaust of Crows Nest. Its 5' exhaust with a Centek muffler, and the way it was done a few decades ago one, the hose coming off the motor is a little long and creates a dip in the exhaust at the front of the 90 that goes to a hose that goes to the muffler. It also forces the hose coming out of the muffler to come down at a slight angle, and that creates the dip. Anyway, I was taking stuff apart, and managed to crack the front inlet on the Centek. The way the hose was, it was probably creating some pressure on the muffler inlet because of the downward angle. I wasn't using what I thought was all that much pressure to take get stuff apart.

Anyway, I talked to a mechanic at the yard, and he told me that I could re-glass it, or get a new one. He also told me that the muffler is made out of fire retardant f'glass, and that the muffler get brittle over time and can crack. Given that an exhaust leak can lead to a sunk boat, I'm probably going new.

Sound right?

[Carl]

If it got real hot I can see it getting brittle...but not so far down the line, your hoses would get charred first. This part is opinion.

As for it cracking...I can see alot of leverage being created on a thin wall fiberglass tube when trying to loosen up those hoses. It is a weak spot and the companies know it as they offer crush collars for the ends so you can crank down on the hose without cracking the fiberglass. To me that is quite telling.

When I bought my boat the prior owner cracked one of the muffler ends trying to snug up the hose. His answer was to silicone up the end, slide hose over and snug a bit. It worked for awhile...at least untill I replaced the exhaust manifolds moving the hose and breaking the seal. I did the same temp fix to get me to the end of the season where I removed the muffler, cleaned off all the old silicone, ground out the cracked area, then glassed using Polyester resin. You have to use polyester as it handles heat, were Expoy resin does not. A couple layers of fiberglass, a little smoothing after it cured and back in service it went. I pulled when converting for larger exhaust...it still looked fine.

As for fire retardant...Stock Exhaust Fiberglass tubes are polyester fiberglass. You can look online to see how they work with them. OR look right here in Captain Patricks Building Tips section. Capt Patrick goes into great detail when he made the Surge Tubes. Those tubes are glassed AND IN FRONT of the mufflers, so they would see more heat then the mufflers being first. I hope its true as I made mine as per his instructions.

If your exhaust angles are wrong and your putting side pressure on the muffler collars...I would consider miter cutting the ends and glassing in line. Or have a glass guy do it for you.

[Tony Meola]

John

With the water flow running thru the mufflers, I doubt they get that hot. Heck, take a plastic water bottle, fill it with water and hold it over a fire. You can boil the water and the bottle will not melt.

I would clean it up and hit it with layers of glass. Like Carl said, do not use epoxy. If you can, I would put a layer of glass on the inside to help stiffen up the break area.

[John F.]

Carl/Tony-

After reading your posts, I figured that since I've f'glassed up a few thru-hulls, I could do this. I'm just about done. Saved me some $$.

Thanks-

John

[Carl]

Those mufflers are stupid money for what they are. I'd hate to see you toss one when only needing a simple glass repair.