Exhaust hose temperature rating

[Ruffles]

I'm amazed that marine exhaust hose is only rated up to 100 C. Fine in normal use but what happens when the inlet blocks? Is something available more robust?

I've recently replaced a short section - the bit between the engine and silencer. It was knackered from repeatedly removing it from the manifold in winter. The new stuff is identical to the old and is marked SAE 100 R4 which appears to be a general standard. The specific standard for marine exhaust seems to be SAE J2006 R2 which appears to be the same but more flexible. But all are only rated up to 100C.

 

[ytd]

they are definitely a bit secondhand when the inlet blocks and the skipper continues on under full throttle to the point of engine seizure, but they don't melt or catch fire. Our first boat had a dry exhaust with the engine and exhaust connected to the motor by a flexible stainless pipe. It made the cockpit floor very hot, was noisy even with a new muffler and I'm sure it leaked a bit of exhaust gas. Much prefer wet exhausts.

 

[cliffordpope]

When I winterised my Yanmar I disconnected the water injection hose and short-circuited it back to a can of antifreeze. I was surprised that the pipe only got mildly warm even running with no water for a few minutes.

 

[vyv_cox]

My water pump failed at a crucial point (don't they always?), right in the middle of the entrance to Scheveningen harbour. I was forced to carry on motoring to get to a position at the shallows inside the outer breakwaters where I could anchor. The engine ran for a couple of minutes after the alarm went off.

Inspecting everything later, the water trap had almost melted right through, whereas the hose appeared to be hardly damaged at all. The trap was one of the moulded plastic ones, polypropylene of something similar.

 

[Strathglass]

In most wet exhausts the temperature rating of the hose is not the critical part.

You don't have to worry about that.

If there is a blockage in the cooling water passage a much more expensive sacrificial part usually forms part of the system (it is a boat after all)

The bit that usually melts first is the first plastic part of the exhaust often the water trap.

Especially if it is one of the Vetus or similar plastic one.

I used to experience it a lot on a hire fleet when punters turned off the inlet water seacock at night and forgot to open it in the morning.

We then got the phone call 'The engine has caught fire, think it's the exhaust'

Iain

 

[Ruffles]

My water trap is the original stainless steel unit. So no worries there. At least until it rusts out.

I thought the better replacement units were high temp fibreglass?

 

[Strathglass]

[ QUOTE ]


I thought the better replacement units were high temp fibreglass?

[/ QUOTE ]

Yes they are, but most chanderlies and marine wholesalers only stock the plastic ones.

Thus there are many more plastic ones than fibreglass ones.

The plastic ones normally give no problems and are generally quite adequate for the job.

Iain