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ť Forum Name: PT Boats - General
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ť Topic: PT Exhaust System Question
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Here's something interesting I've noticed. On early 103 class Elco's there is a tubing that comes out of the stern and into each of the exhaust pipes on the exterior of the boat. This feature is gone on later models. I don't see it in any photos past PT-117. I'm adding this detail to my models but I'm wondering what they are. Here's some photos illustrating what I'm talking about...

[IMAGE]http://i108.photobucket.com/albums/n27/David_Waples/PT%20BOATS/PT-117stern.jpg[/IMAGE]
[IMAGE]http://i108.photobucket.com/albums/n27/David_Waples/PT%20BOATS/SternPT-109.jpg[/IMAGE]

Any thoughts?
Dave

David Waples

Posted By: David Waples | Posted on: May 9, 2010 - 8:45am
Total Posts: 1679 | Joined: Jan 2, 2007 - 9:55pm

David,

Probably a water pipe for cooling the exhaust. The exhaust system was cooled with a water spray along the length of the pipe from the engine exhaust manifold to the transom. I would assume that this pipe is one of the water inlet pipes. I would also assume that it was deamed not neccesary to have this cooling pipe and removed to reduce boat constuction costs.

The ELCO drawings show this system and I will need to review the drawings to determine if my suposition of the pipe fundtion is correct.

Bill Smallshaw

Posted By: smallwi | Posted on: May 9, 2010 - 9:13am
Total Posts: 134 | Joined: Jun 21, 2007 - 3:02pm

These are listed as 'Salt Water Connections' in the ELCO blueprints. There were a number configurations of these tubes based on which boat number one is modeling. For example for the 157 I used the drawing ELCO_Roll_5535-4_72SCAN_00473.pdf from the Dick Washichek collection of ELCO PT drawings. This drawing covers PT-147-162 and PT-139-145. Looks like you'll use ELCO_Roll_5535-4_72SCAN_00467.pdf

This tube appears to be a by-pass tube that connected to the flapper valve collar thru the transom to the exhaust pipe inside the engine room. See drawing ELCO_Roll_5535-4_72SCAN_00461.pdf (as an example) of the routing.

Thanks again to Dick Washichek to helping every PT admirer/researcher/historian/modeler with his efforts on these library of drawings and making them available to us all.

Bridge

Posted By: TheBridge | Posted on: May 9, 2010 - 9:31am
Total Posts: 318 | Joined: Nov 22, 2009 - 3:04pm

I don't really have an answer to this question. The 167 did not have water cooled exhausts, but we were aware that some boats did. Long high speed runs made the exhaust pipes dangerously hot. We had more than one crewman hospitalized when he was bounced into a hot pipe.
Keeping anything inflamable away from the pipes was critical and there were worries that the mounting of such overheated objects to the wood could cause a fire.This was particularly worrisome on our boat because the Skipper insisted everyone take turns in the engine room. We never experienced a real fire.

Posted By: BobPic | Posted on: May 9, 2010 - 1:09pm
Total Posts: | Joined: Unregistered

Hi guys,
Could it be possible that this water cooling was for cooling the damper valve pivot bearing? I know it would get hot, and cooling it may have been in order to prevent it from sticking or jamming. Maybe they discovered it was not needed and then discontinued the arrangement on later boats. I bet Dr. Al Ross or Frank Andruss would know some more details!

Similarly, on PT658 we originally installed insulated but uncooled exhaust stacks, but they got so hot that one actually ignited the nearby wood inside the engine room. After that we copied the original Higgins method of a water cooled pipe within a hose. The new water cooled stacks rarely get warmer than 100 degrees, but we need to ensure we have positive flow when we first start the engines. I have read several instances where Higgins boats blew an exhaust stack due to losing water flow in one of them. (Sometimes the seawater circulating pump on the engine loses prime). We take special care not to let this happen to us!

Just my 2cents! Jerry PT658 Portland OR

Jerry Gilmartin

Posted By: Jerry Gilmartin | Posted on: May 9, 2010 - 1:39pm
Total Posts: 1472 | Joined: Oct 8, 2006 - 11:16pm

Boy, good question. I appreciate Jerry's faith in me that I would know the answer. I do know that the 4M-2500 Packard Marine engine was cooled with both Fresh water and Salt water through pumps.

These pumps would cirrculate (for instance Sea water) to cool the exhaust manifold and pipe whenever the engine was operating at speed or at rest. From the salt water pump the sea water is piped to the exhaust manifold water jackets. Entering these jackets from the reverse gear end, water flows through them, and would come out at an elbow at the superchsrger end of the exhaust manifold. This Sea water was then conducted into the exhaust pipe water jacket, where it cooled the pipe and exhaust gases. The Sea water would finally be dischared over-board through the exhaust pipe outlets. What you are seeing is par of that cooling pipe...............

Posted By: Frank J Andruss Sr | Posted on: May 9, 2010 - 5:36pm
Total Posts: 3497 | Joined: Oct 9, 2006 - 6:09am

I checked the ELCO drawings again. It is just a single pipe that is connected to the flapper collar, goes through the transom board and connects to the bottom side of the exhaust pipe within 1 to 2 feet. That's it! Curious isn't it.

Posted By: TheBridge | Posted on: May 9, 2010 - 7:47pm
Total Posts: 318 | Joined: Nov 22, 2009 - 3:04pm

I checked the ELCO drawings again. It is just a single pipe that is connected to the flapper collar, goes through the transom board and connects to the bottom side of the exhaust pipe within 1 to 2 feet. That's it! Curious isn't it.

Posted By: TheBridge | Posted on: May 9, 2010 - 7:48pm
Total Posts: 318 | Joined: Nov 22, 2009 - 3:04pm

Hey Bridge,
That makes a lot of sense. On our boat, the exhaust pipes cooling water also exits the exhaust pipe just inside the hull of the boat and then connects to the bronze exhaust casting (where it is connected to the exhaust hose). I think somebody told me that was to help the joint between the hose and the casting remain at similar temperatures so that it would not loosen. Inside the boat, the exhaust hose end is held onto the outside of the casting by hose clamps so this would make sense if there was a similar arrangement on the Elco exhaust pipes/hoses. Keeping that Exhaust flange at the same temperature as the exhaust hose is a good thing. So your explanation makes sense. Jerry

Jerry Gilmartin

Posted By: Jerry Gilmartin | Posted on: May 9, 2010 - 8:04pm
Total Posts: 1472 | Joined: Oct 8, 2006 - 11:16pm

After the small pipes lead into the exhaust tube jacket the water dumps into a water jacket that wraps around the outboard side of the mufflers and then into the mufflers through a series of holes. The jacket is hard to see in most photos, it goes down to 13.5" below the butterfly valve shaft and is about 2.5" wide as viewed from the aft looking forward.

The salt water pipes leading to the mufflers had a small design change after the 138. Another drawing is for the 139-145 and 147-162. I'm not sure after that or the design for the 146 but I think later boats fed into the exhaust tube jacket before they exited the transom.

Posted By: Jeff D | Posted on: May 9, 2010 - 10:58pm
Total Posts: 2200 | Joined: Dec 21, 2006 - 1:30am