The PT Boat Forum
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ť Forum Category: PT Boats of WWII
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ť Forum Name: PT Boats - General
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ť Topic: Elco PT boat exhaust systems
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Dear Forum, I am interested in the exhaust pipes of the PT boats. At least on the Elco PTs, they were located on the stern and the exhaust pipes which turn down to below the water line, appear baffled which I assume allows the boats to move quietly at slow speed while approaching enemy shipping and then opening the baffles to allow exhausting to the air above the water line when they needed to run at high speed. My questions are, is this why they were designed as such and secondly, was this unique technology to the PT boats or did other small naval military vessels have muffler/exhaust systems like this? Thanks for you input. Lee Greenwood

Posted By: Lee G | Posted on: Aug 15, 2017 - 5:04pm
Total Posts: 16 | Joined: Dec 6, 2015 - 10:11am

Hello Lee,
First of all welcome to the Forum!

Question 1: Why were PT Boats designed to have mufflers? Like you said the mufflers were used only when the Engine was running at Idle speed. Before increasing the throttle position, the first step was for the Motormac to Fully Open the Damper Plate. This would prevent the baffle plate from being blown off the end of the pipe. It was to primarily used to reduce the sound of the running engines when "Laying to". Evidently the sound carries across the open water at night.

Question 2 Was this unique technology to the PT boats or did other small naval military vessels have muffler/exhaust systems like this?
I have no idea what other boats did, but I have never heard of other small craft in the USN using mufflers.
I hope this helps.

Jerry Gilmartin
PT658 Crewman
Portland OR

Posted By: Jerry Gilmartin | Posted on: Aug 16, 2017 - 2:29pm
Total Posts: 1473 | Joined: Oct 8, 2006 - 11:16pm

Turns out this is a timely question in a way for me also. My question is was there a noticeable difference is the sound between an Elco and a Higgins when both were operating muffled, all things else being equal? The reason I ask is the Elco's have what looks to be a marine version of an early automobile muffler the exhaust goes through prior to exiting under water. The Higgins on the other hand had what appear to be a simple butterfly valve that directed the exhaust from exiting parallel to the surface, to exiting perpendicular to the surface when muffled. Logic tells me the Elco would be quieter, can anyone confirm this?

Larry
62 Bel-Air
260 Eagle EXP
79 Cole TR-2
2016 Corvette Z51

Posted By: bubbletop409 | Posted on: Aug 16, 2017 - 9:44pm
Total Posts: 164 | Joined: Apr 22, 2013 - 11:48pm