Mufflers on the 38 with 454s.

Mufflers on the 38 with 454s.

Joined: December 20th, 2007, 5:01 pm

February 11th, 2008, 3:53 pm #1

Commadores:
Next to get done is to replace the big cast iron mufflers for the two 454's in the Summer Palace. I notice that there are two types of fiberglass mufflers offered. One is an in-line type and the other is a top exit model. Our cast iron mufflers are the inline type. What are the pluses and minuses of each type beyond the obvious? I can see that it is easier to get the inlines hung well above the water line. There is also a cast iron muffler for the Koler genset. It may be original as it has the Chris Craft logo cast into it. Depending on what it looks like, it too may have to go.

I have noticed there are newer (than the galvanized pipe fittings) fiberglass 45 elbows that collect the two hoses from the risers and feed to the mufflers for each of the engines. Isn't the water exiting the risers too hot to be using fiberglass? It would seem best to use some galvanized fittings and nipples there, or stainless even better.
Thanks,
Jerry
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Paul
Paul

February 11th, 2008, 4:25 pm #2

There is a major safety concern about the older series boats that used galvanized iron collectors. They are all failing now. The results can kill you in more than one way.

Bruce Martin has a nice thread showing how he fabricated stainless steel collectors. I have a thread on how I used a copper collector and then transitioned with a fiberglass elbow.

The fiberglass elbow, by the way, utilizes high temp resins and they're very capable of handling the service as long as there's water in the system. If not, they'll burn up just like your rubber hose will.

Here's some good references for you, if you're designing an exhaust system.

Safety Alert regarding rusti-out of old exhaust systems
http://www.network54.com/Forum/424840/m ... 1175813057

Exhaust conversion thread
http://www.network54.com/Forum/424840/m ... 1135648234



These parts, except for the copper, are from Exhaust Systems of Alabama, a very good source of fairly priced parts, but they don't take credit cards (personal checks are okay).

http://www.network54.com/Forum/424840/m ... 135870359/
Here's a 5-second video shoing water going through my fiberglass 90-degree



Regards,

Paul

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Joined: December 20th, 2007, 5:01 pm

February 11th, 2008, 5:11 pm #3

Paul:
You put in a nice system. Thanks for the response regarding the accumulators. It has been suggested that two 45s with a short nipple would be better than a 90 because they would not add as much back pressure as the 90 might. Obviously yours is working. What's your opinion now?

I am still researching the muffler type, but whichever, it seems that fiberglass is the way to go.
Jerry
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Paul
Paul

February 11th, 2008, 5:30 pm #4

Hi Jerry,

I don't think the back pressure difference of a 90 has any real bearing on a system that fills a cast iron tank full of water like the CC muffler system does. For me, I don't think it's an issue at all. I rarely run the motors fast enough where I have any real world consideration about back pressure.

I know when Warren Pateman installed his diesels, he had some concerns about back pressure and they measured it with some sort of an instrument. Thats beyond what I'm doing as a hobbiest. Looking at the system I took out, and the one I installed, I'm not losing any sleep.

In addition, my philosophy of "less is more" is as follows: The fewer fittings and hoses you have in the system, the less likely you are to have a fitting or joint prone to failure. In that regard, less may well provide more safety and relliability. I evaluated that when I did my installation. If you were able to see the video, you can see a shocking amount of water in the system, and that's how it runs at idle. This is partially due to the flow, and the height of the discharge pipes, etc. At speed, everything blows through that 4-1/2" diameter pipe and if there's any backpressure, it's probably created by the muffler and not by the 90. If you look closely, you'll see that 90 is actually segmented, so it functions a lot smoother than a true 90.

Just a couple of thoughts.

Regards,

Paul
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Don
Don

February 12th, 2008, 12:11 am #5

Commadores:
Next to get done is to replace the big cast iron mufflers for the two 454's in the Summer Palace. I notice that there are two types of fiberglass mufflers offered. One is an in-line type and the other is a top exit model. Our cast iron mufflers are the inline type. What are the pluses and minuses of each type beyond the obvious? I can see that it is easier to get the inlines hung well above the water line. There is also a cast iron muffler for the Koler genset. It may be original as it has the Chris Craft logo cast into it. Depending on what it looks like, it too may have to go.

I have noticed there are newer (than the galvanized pipe fittings) fiberglass 45 elbows that collect the two hoses from the risers and feed to the mufflers for each of the engines. Isn't the water exiting the risers too hot to be using fiberglass? It would seem best to use some galvanized fittings and nipples there, or stainless even better.
Thanks,
Jerry
Jerry, The fiberglass pieces are made with flame retardent resin made for exaust use.


Don
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Joined: December 20th, 2007, 5:01 pm

February 12th, 2008, 1:24 pm #6

Don:
Thanks for the clarification on the constuction material. I am going with the resin and rid my life of rust. ( Pictures to follow next week.) I am still curious why there are two types of mufflers, the straight thru and the vertical lift. Is the answer no more than where or how it is to be used? I used the vertical lift type on my sailboat because I needed to get the exit hose above the water line and this seemed a good way to do it, but I could have used a straight thru just as easily, or more so because I had to build a base for the muffler to sit on. On my Commander, the cast iron muffler is hung above the water line and replacing it is simple with the in-line type. There is also a price difference. Does it matter whether the exhause is from gas or diesel (a tempature difference)? Or is it a space issue. The vertical lift muffler takes up more deck space below. I am making this too big a deal, but still curious.
Jerry
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Dave Mehl
Dave Mehl

February 12th, 2008, 2:15 pm #7

I'm running original 431 Lincolns in mine, they run great but the mufflers began having problems (called leaks). On a 38, at least on mine, the exhaust flow is out of the motor and almost flat, right out the tailpipe, so to speak. Your risers are therefore the only thing keeping backwash from getting in your motor, since they form a dam to keep the flood back when you turn off the ignition. I always wondered if I cut the motors dead while underway, and the boat lurched forward, would the internal water overcome the riser and flood out the motor. Fortunately over the years this has never happened. You have to be careful so your flow is down and away from the risers if possible, so water will pocket down and not sit against the inside of the riser, just waiting to drip drip drip into the motor. A slight upturn to blast through the muffler would appear to be okay. It's been so long since I did mine, I can't recall just how it was done, but it has been working. I used the flow-through resin fiberglass jobs, and never had any problem since. They looked like a giant cherry bomb muffler. Be sure you let the sales person know what you're going to use it for when you buy, I'm sure they sell a lot of them for the 454 size motors.

Dave
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James Brunette
James Brunette

February 12th, 2008, 8:28 pm #8

Commadores:
Next to get done is to replace the big cast iron mufflers for the two 454's in the Summer Palace. I notice that there are two types of fiberglass mufflers offered. One is an in-line type and the other is a top exit model. Our cast iron mufflers are the inline type. What are the pluses and minuses of each type beyond the obvious? I can see that it is easier to get the inlines hung well above the water line. There is also a cast iron muffler for the Koler genset. It may be original as it has the Chris Craft logo cast into it. Depending on what it looks like, it too may have to go.

I have noticed there are newer (than the galvanized pipe fittings) fiberglass 45 elbows that collect the two hoses from the risers and feed to the mufflers for each of the engines. Isn't the water exiting the risers too hot to be using fiberglass? It would seem best to use some galvanized fittings and nipples there, or stainless even better.
Thanks,
Jerry
PT Boat mufflers, designed to allow the boat to go into stealth mode, and then to be opened up for open-pipe running. Those Packard PT engines had two rpm ratings, one was the max allowable rpm, and then there was another rating cast into the block. It was the "emergency wartime maximum rpm".



Stowed on board the "Liberty Ship" Joseph Stanton, at the Norfolk Navy Yard, Virginia, 20 August 1942. Note heavy bracing at the PT boat's stern and on her deck, to prevent movement as she is transported to the Pacific. Also note her torpedo tubes, engine mufflers and 20mm gun mount, with "109" painted on it.

JB
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Don
Don

February 12th, 2008, 11:06 pm #9

Don:
Thanks for the clarification on the constuction material. I am going with the resin and rid my life of rust. ( Pictures to follow next week.) I am still curious why there are two types of mufflers, the straight thru and the vertical lift. Is the answer no more than where or how it is to be used? I used the vertical lift type on my sailboat because I needed to get the exit hose above the water line and this seemed a good way to do it, but I could have used a straight thru just as easily, or more so because I had to build a base for the muffler to sit on. On my Commander, the cast iron muffler is hung above the water line and replacing it is simple with the in-line type. There is also a price difference. Does it matter whether the exhause is from gas or diesel (a tempature difference)? Or is it a space issue. The vertical lift muffler takes up more deck space below. I am making this too big a deal, but still curious.
Jerry
Jerry,

you probably want to stick with inlines the aqua lift type is for installations where the engine is below waterline. when I started gutting my boat I found the side up against the side ofthe boat was gone!

Don
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Paul
Paul

February 12th, 2008, 11:54 pm #10

Guys, I sure don't want to be held to this, but I sort of a gree with Dave's comments, about the flow of water out of the boat (on a big block 38), downhill from the riser right through the muffler. An aqua lift situation may well provide more protection, especially in a following sea or diagonal wave that would smack up against the exhaust port and want to force water into the motor. Take a look at my installation, you can see it's "almost flat" and I'll have to put a level on it to really see which way the water flows when she's sitting at the dock.

For my purposes on the inland waterways, the backwash issues due to waves never entered into the equation. I'm still using original iron mufflers, they're still working as intended, and I don't think the system is lifting any water (it appears to be pushing it sideways away from the riser during the time the motor is running. I'll have to check this real close next time I'm aboard, because I'm very interested in the true flow here, and I don't want any water backing up against the riser while the boat is sitting, as Dave suggested.






Regards,

Paul
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