That "scare story" comes from Bob Brandenburg, TIGHAR's radio expert, not a boiler operations expert.
TIGHAR's Bob Brandenburg is LCDR Robert Brandenburg USN (ret), a career naval officer who, among other things, captained a Destroyer Escort during the Vietnam War. I'm sure he'd be happy to compare his knowledge of boiler operations at sea with yours any day.
See what I wrote about this before at: https://tighar.org/smf/index.php/topic,383.msg4989.html#msg4989
In that posting you wrote:
"But this is all a theoretical discussion and we do not have to even consider it since there are all the contemporary eye witness accounts and documents saying that the smoke screen was there for hours, it stretched more than ten miles down wind and would have been visible for 40 miles."
All of the Coast Guard and Navy after-action reports include heavy-doses of not-our-fault, blame-the-victim. Factual errors and false assumptions abound. There was also a noticeable element of getting-our-story-straight. Commander Thompson's (CO of Itasca) "Radio Transcripts Earhart Flight" is the worst of the lot. Many, but by no means all, of the inaccuracies and self-serving distortions in the official reports are described and documented in Finding Amelia.
Elgin Long even includes a photograph of the Itasca making smoke and you can see the quality of the smoke for yourself.
The gentleman's first name is spelled Elgen. He captions the photo in his book:
"The Itasca makes smoke as boats bring ashore a landing party to assist Earhart on her arrival. Note how the smoke lies on the surface and dissipates as it drifts away." The caption is in error. We have the same photo. It came from Itasca's quartermaster Frank Stewart (now deceased). The photo was taken in 1936 during one of Itasca's earlier trips to Howland. The ship is not laying down smoke for Earhart. She's apparently "blowing tubes."
I don't know how long Itasca made smoke but I don't think it matters anyway. I think the available evidence strongly suggests that Earhart was never close enough to see any smoke short of a nuclear test.