Expected life of Flexible Rubber Exhaust Pipe.

[Jim@sea]

The boat I have just bought is 15 years old with under 500 hours.
The 4" Flexible Rubber Exhaust Pipe has obviously deteriorated over the years and has split just above the large Jubilee Clip, this side of the Exhaust Outlet and started squirting water into the bilges.
Although obviously I am aware that with cars Cambelts should be changed every 3 years or 30,000 miles, but until now I was not aware that a Flexible Rubber Exhaust Pipe could fail. Certainly where it has not failed it has gone extremely brittle and is no longer flexible.
Certainly its failed in such an inaccessible place that a temporary repair would be impossible to do on a voyage.
Perhaps the previous owner had not noticed that the Automatic Bilge Pump had been getting rid of the water or it had gone worse in the half hour that I was running the engine fed by a hose pipe.
So has Flexible Rubber Exhaust Pipe a suggested replacement change date and has anyone else had this problem.

 

[Latestarter1]

I think you are on the wrong track.

Flexible rubber exhaust hose, now there is an oxymoron!

There are two issues at play when it comes to exhaust system durability.

#1 Spray head design. Theory is real simple, the spray head in the riser SHOULD distribute the cooling water evenly around the inside of the exhaust hose to prevent hot spotting. The basic principals of how to achieve this is lost on some engine manufacturers and certainly many installers.

The Fairline Princess and Sunseeker use systems designed and built by Hallyard or Manuflex and generally object lessons in design and execution. However much of the time stuff out there is a complete pile of poo put together by some clueless couch engineer.

#2 Hose failure could be related to past raw water pump failure or the dreaded sea cocks shut start up. Previous owner may have thought 'phew got away with it!' Damage was done, just stored up waiting to bite somebody in the bum in the future.

Natural hose aging generally manifests itself by internal delamination, causing its own set of issues. Not your failure mode, hose become brittle is due to excess heat.

Action plan;

Strip out raw water side completely and look for debris resulting from earlier raw water pump failure.

Remove the riser and take a detailed look, 15 years, it may be showing signs of terminal decay with spray holes blocked with corrosion or water actually finding its way into the exhaust through internal corrosion, bypassing spray head completely.

Just replacing the hose without a complete investigation into the cause will bite you again.

 

[nedmin]

If you can its not a bad idea to remove hose say after 5 years and swop it round.

 

[Latestarter1]

If you can its not a bad idea to remove hose say after 5 years and swop it round.

You obviously have never tried fighting this filthy stuff! Once it gets a set then ages no longer flexible.

If exhaust is properly designed a pointless dirty exercise.

 

[DAKA]

The boat I have just bought is 15 years old with under 500 hours.
The 4" Flexible Rubber Exhaust Pipe has obviously deteriorated over the years and has split just above the large Jubilee Clip, this side of the Exhaust Outlet and started squirting water into the bilges.
Although obviously I am aware that with cars Cambelts should be changed every 3 years or 30,000 miles, but until now I was not aware that a Flexible Rubber Exhaust Pipe could fail. Certainly where it has not failed it has gone extremely brittle and is no longer flexible.
Certainly its failed in such an inaccessible place that a temporary repair would be impossible to do on a voyage.
Perhaps the previous owner had not noticed that the Automatic Bilge Pump had been getting rid of the water or it had gone worse in the half hour that I was running the engine fed by a hose pipe.
So has Flexible Rubber Exhaust Pipe a suggested replacement change date and has anyone else had this problem.

Exhaust like bellows in the engine bay ?
One of mine went 1st trip out this year, swmbo noticed the bilge pump on so I had a good check when we got in, no leak on tick over, nearly ignored it but checked @ 1500rpm and found a small split.

I replaced both sides and kept the good one as a spare.

Several years previously a pucker cummins agent had tightened a jubilee clip 1/2 on the flange which cut into the rubber causing premature failure .

Now I am a little concerned if laterstarter or a mechanic wouldnt mind commenting please ..........

On one side I had a bit of spare length and being concerned not wanting to repeat the same mistake as the Cummins mechanic, I deliberately made sure I pushed my hose on a long way, but could I be causing water to get behind the exhaust hose and cause corrosion on the aluminium (?) exhaust ?
Do I need to be exact and fit it very close to the end ?

(in other words I have deliberately over lapped the aluminium exhaust. does it matter)

 

[nedmin]

Swapped it over last year ! It was still flexible so obviously a good installation.Still I,ve only got 1 engine so can get at it easily.Used to have 2 engines got sick of struggling as I get older.

 

[david_bagshaw]

salty bung

Running engine on a hose...


I had the same, when we first took over the present boat.

Was suprised to find a heavy leak where a week previously there had been none,

came to the conclusion that salt crystals bunged up the hole, and the fresh water from the hose.....washed away the salty bung!!!

 

[Latestarter1]

Come on guys...........This tubing is pressurised to almost 1 psi on a GOOD system, failures are the result of hot spotting, salt crystals witholding 1 psi!! Indicates a defect somewhere in the system, or flaw in system design. Simple aging results in internal delamination.

OEM supplied spray heads have finite life, 15 years old and I would consider a serious look inside.

Gravity and care result in good systems, spray pattern has to be even, with careful spray head design.