fiberglass exhaust collectors to replace monel

[MikeP]

I know this has been discussed in the past and there is was a good bit of input that FG collectors were better, lasted longer, etc. I was concerned re the use of FG where Hatt originally used monel but I was prepared to accept that FG was OK based on input that folks had switched.

However, the guy who is DOING the FG exhaust work has expressed concern that FG is not the proper material for this particular application - our 1980 53MY 8V71TI motors. He is concerned (as was I originally when this first came up a couple of years ago) that the heat generated at WOT by the turbomotors may be too high. So I'm wondering if anyone has used FG to replace the metal collectors on this same application. I don't know if the collectors on all hatts with 8V71Tis are the same or not so I don't know whether FG collectors may work fine in one Hatt but not another...

 

[Genesis]

If you're talking about the elbow that transitions from the showerhead to the muffler, I had fiberglass ones made after my Monel ones rotted.

Remember, these things are sitting on a WOOD support (at least they were in my boat); if they get hot enough to deteriorate (especially metal ones!) you got bigger problems.

I had no problems at all.

 

[MikeP]

Yeah, that's what I'm talking about. On our 53MY the collector is a big, awkward one-piece three dimensional "Y" looking thing with a couple of surge tubes as well. The first thing after the showerhead is a rubber hose to connect the collector to the showerhead so it seems that even in the oem setup, the rubber could catch fire in a catastrophic situation. Though if it did, there isn't that much to burn and nothing non-metal around it. On our 53 all mounting supports are metal - there is no wood involved at all.

The oem collector has alarm temp sensors mounted to it; can they be mounted on the FG collector and provide useful info or would the FG be on fire before the sensor could detect it?

 

[MarioG]

Mike, a friend of ours has a 46c with 8v92s. he has the fiberglass collectors. they look real nice and seem to be trouble free.

 

[REBrueckner]

I seriously doubt anyone has MONEL exhaust components, but if you can really get MONEL, go for it: they should last forever unless faulty welds become a weakspot.

Stainless steel is characterized by its chromium content, monel by its nickel content.
http://en.wikipedia.org/wiki/Monel

http://en.wikipedia.org/wiki/Stainless_steel


I'm not an expert on exhaust materials, but I'll bet ones that burn out are an (inappropriately active) alloy of stainless steel, not "monel"...that's what was widely used beginnging around the 1970's on some Detroits....I happened to have copper alloy risers (curponickel, I think)

(http://en.wikipedia.org/wiki/Cupronickel)

on 1961 6V53's and for whatever reason that vintage copper alloy outlived the "premium" stainless steel alloy by a wide margin.

After burning out several black iron exhaust elbows every other year on a 1961 Onan generator, I switched to commercially available stainless steel pipe: it stood up perfectly to diesel exhaust, heat and salt water for over 15 years....

Notice the premium alloys seem to be characterized by the presence of nickel...and it an't cheap.....

 

[Genesis]

No, these were monel. On my engines (6V92 TTs) the crossover pipe ("Collector") was hot (insulated, OEM with blankets, the replacement I bought was dry-wrapped) and stainless steel. The showerhead was on the end of that (integral), then a piece of blue silicone hump hose (vibration isolation), then the elbow, then a longer piece of straight hose to the muffler.

The OEM elbow was monel. My options were to replace with the original material (God-awful expensive) or fiberglass with SS compression rings at the joint points (somewhat God-awful expensive.) I went for the latter and had zero trouble with it. The OEMs were literally original and lasted 20 years - I'd call that decent service life.

The overheat sensor should not be on the elbow - it should be on the showerhead. My boat had a "pad" welded to the showerhead with two screwholes for mounting the sensor to and I specified that the replacement was to have the the same mounting and geometry.

 

[MikeP]

"The overheat sensor should not be on the elbow - it should be on the showerhead."

You are absolutely right, Karl, they are on the showerhead. In my mind I had pictured them on the collector but until a few minutes ago, I hadn't actually looked at them since getting back on the boat yesterday. The FG guy is coming over later this afternoon so we'll talk a bit more about it and go from there. It makes me feel a bit better realizing that the alarms will still function normally.

That being said, one of my friends here at the dock said that he had trouble twice with FG exhaust tubing. Once the RW pump failed and it burned a hole through the tube and another time the RW itself wore a hole in the FG from abrasion. Water erosion DID create the Grand Canyon...

 

[Angela]

We have fiberglass collectors on our 8V92TI - no problems.

 

[Genesis]

If you have overheat alarms on the showerheads, and they're WORKING, you will know instantly if raw water flow is interrupted (like 2-3 seconds after it happens.)

The risks if you keep operating without raw water flow are extreme; it's not just the fiberglass tube, but the risk of setting the mufflers on fire. If you manage to do that you're going to lose the boat as there's almost never a way to get in there and put it out. It is for that reason that I believe ALL wet exhaust systems NEED a temperature sensor on the showerhead.

 

[takefive]

FWIW, I removed my collectors about 2 monthes ago, they had a metal disk welded on them which said 'Kay Industries, Detroit, 316L'. Assume these were original, was informed the 'L' designates low carbon stainless. I got lucky there was only one perforation per collector, the rest of the material seemed too be in great shape(fingers crossed). Any way had a guy do some spot TIG welding too fill holes then TIG a patch on each spot repair. Wanted to go with FB, just took the cheapest way out.

 

[bostonhatteras]

if you are that concerned about heat you can make your own heat sensors. just look up "snap switch" on google. it is a type of switch that can operate how ever you order it. normally open, or closed. different temp settings. it operates on a bimetal concept. rig this up to a buzzer and 12 volts and use any material you want. the alarm you made will alert you to any issues. home made heat alarm.

 

[captddis]

If you have overheat alarms on the showerheads, and they're WORKING, you will know instantly if raw water flow is interrupted (like 2-3 seconds after it happens.)

The risks if you keep operating without raw water flow are extreme; it's not just the fiberglass tube, but the risk of setting the mufflers on fire. If you manage to do that you're going to lose the boat as there's almost never a way to get in there and put it out. It is for that reason that I believe ALL wet exhaust systems NEED a temperature sensor on the showerhead.

Have you ever actually seen a fiberglass tube catch fire? They are made of fire retardent resin and in 35 years of working on exhaust systems, never seen one catch fire. Scorch and cook resin out but never a fire. I have seen exhaust hose melt and the fiberglass tube was intact. They use fiberglass tape to wrap dry exhaust systems.

I would have no worries using a fiberglass collector.

 

[Boatsb]

Fiberglass does not burn. It will eventually melt but Captdis is correct about the fire retardant resins. If you build them right there will not be an issue. The glass will take a lot of heat and also not corrode. That's why someone I know just put in fiberglass surge tubes for his bert.

 

[SKYCHENEY]

Have you ever actually seen a fiberglass tube catch fire? They are made of fire retardent resin and in 35 years of working on exhaust systems, never seen one catch fire. Scorch and cook resin out but never a fire. I have seen exhaust hose melt and the fiberglass tube was intact. They use fiberglass tape to wrap dry exhaust systems.

I would have no worries using a fiberglass collector.

I have loose fiberglass insulation inside of my wood stove. It was designed that way. There is a stainless baffle right on top of the fire and it is filled with fiberglass insulation. As stated, that stuff will not burn. It is the resin that you have to worry about, not the fibers.

Ask about what resin will be used and get the specs on it.

 

[MikeP]

"Fiberglass does not burn."

Uh...what about Corvettes that burn to ash on the side of the road or FG boats that do the same when there's a fire?

 

[captddis]

UH... The tubes are made with fire retardent resin. After a fire the cloth is still there albeit shredded.

 

[Boatsb]

what captdis said.


FYI it gets brittle and crumbles from the extreme heat but the fibers do not actually burn. They are glass and therefore non combustible.

 

[captddis]

"The overheat sensor should not be on the elbow - it should be on the showerhead."

You are absolutely right, Karl, they are on the showerhead. In my mind I had pictured them on the collector but until a few minutes ago, I hadn't actually looked at them since getting back on the boat yesterday. The FG guy is coming over later this afternoon so we'll talk a bit more about it and go from there. It makes me feel a bit better realizing that the alarms will still function normally.

That being said, one of my friends here at the dock said that he had trouble twice with FG exhaust tubing. Once the RW pump failed and it burned a hole through the tube and another time the RW itself wore a hole in the FG from abrasion. Water erosion DID create the Grand Canyon...

Well, if water erodes fiberglass all of our boats should have no bottoms left in them.

 

[Boatsb]

What are all the water slides made of?

 

[Genesis]

The glass won't burn but the resin sure as heck will. It will also melt.