Expanding wet exhaust hose?

[lituya1617]

You cannot put ten pounds of manure in a five-pound sack. Don't force the hose! You will damage it and it might slip off and sink your boat! Get the correct size.

[Manateeman]

Correct. If it’s got wire, it will split or delaminate as it ages.
I don’t think Oil of Olay will prevent these wrinkles.
Happy trails to you.
Mark, manatee applying sunscreen

[StuartWeibel]

I'm surprised that most of the posts in this thread suggest means of making a 2 inch hose work in place of a 2 1/8 inch hose.

Yes, if you can manage it, it will probably work for a long time. Until it doesn't.

Certainly no engine manufacturer would condone such a fix.

The prudent thing to do is change out the hose, which, yes, also means changing out the through-hull fitting... Expensive and painful.

Exhaust systems on a boat are mission-critical and a bit of black magic. The following article may give you useful insights into how all the pieces fit together

http://www.goodoldboat.com/reader_se...ne_exhaust.php

[Manateeman]

Correction. I posted Miami . The company is DeAngelo in Fort Lauderdale.
Not cheap but excellent work.
Sorry, I’m an old, slightly forgetful manatee.

[jimbunyard]

For those who predict eventual premature failure induced by stretching 2" hose over a 2 1/8" fitting, perhaps you should consider a few things. The hose under consideration is rubber, with a woven and (probably) single spiral wire reinforcement. It is designed to be flexible, though not as much as with woven-only reinforced hose. As I understand it, the spiral wire is intended primarily to avoid kinking, though there may be some component of expansion restriction involved as well.

Regarding feared delamination issues, though the vectors are a little different, the 'stretching' concerns might be better directed elsewhere. For instance, forcing the hose over a 1/8" increase in diameter causes the perimeter of the hose to stretch by .39" (which surprised me) or about 6%, while a 4" radius bend (8" circle) causes the hose to stretch about 6", or 25%.

The reason a 4" radius is important is that I'm assuming that is about the mininum bend radius for a 2" spiral wound exhaust hose. If that radius is take from the inside, then the outside radius will be 5" (25%), which means that the inside wall radius rubber/reinforcement matrix is compressed by X amount (don't know how to figure that), while the outside wall radius rubber/reinforcement matrix will be stretched by about 6.25", or in RM's case by about 3 1/8" because his bend is only 180 degrees.


I'm guessing the real eventual failure will be caused by the 180 bend and the erosion of the inner wall of the hose at that location by sediment in the raw water and carbon in the exhaust long before any failure from stretching-induced delamination issues at the exhaust elbow connection.

And even that'll be a long way down the road --- er --- waves.


Leaving out the 'argument from authority' of how many times many of us have done this.

[Manateeman]

Hi. Delamination of rubber hose and subsequent hose failure is simply a function of temperature, exposure to ozone and the number and magnitude and range of flex cycles. The suggestions to stretch an incorrect size hose is just wrong and will shorten the useful life of the hose. This is especially true of wire hose.
I worked for the chief research engineer of Spaulding sporting goods for a short time and I learned a lot about rubber. Basket, tennis, foot, soccer, hand, golf...Spaulding knew rubber technology. This was before the popularity of silicon rubber. Hose, tires, tennis...flex fatigue and the delamination of rubber from fabric was a well studied subject. Heat is how you make things with rubber and how rubber parts are destroyed. Why would major consumers of hose move away from traditional rubber to high technology silicon formulations.
In marine applications, wire rusts, expands and delaminates the hose internally.
It’s difficult to inspect from the exterior. Small cracks in the outside layers let water reach the wire and failure follows. Why induce pressures on the hose lamination boundary area simply because you find it difficult or costly to get the right diameter hose. Failure caused by stretching won’t leak a little water, it might leak a little carbon monoxide . It doesn’t take a lot to kill you.
Exhaust systems should be as strong and corrosion resistant as possible. They should be inspected and contain few flexible sections. Lastly, a CO alarm in every cabin. I recall an incident of a young woman who died from CO while taking a shower in her yacht due to a heater exhaust leak. No shortcuts please.
Happy trails to you.
Mark, a boatbuilding manatee