Replacing my exhaust and how to choose a hospital silencer?

[Tonka]

As you are in Middlesex then the place to go for exhaust pipe is T Norris & Sons in Isleworth . They will see you alright and not rip you off

[jetzi]

9 hours ago, Cheshire cat said:

I'm looking forward to seeing the photos on Tuesday!

I hope I don't disappoint!!

8 hours ago, Tonka said:

As you are in Middlesex then the place to go for exhaust pipe is T Norris & Sons in Isleworth . They will see you alright and not rip you off

Ah, thank you for the recommendation but I have already placed my order with TW Marine. I am very pleased with their service so far and their silencers come with a recommendation, so let's see!

[jetzi]

On 21/08/2019 at 12:30, Cheshire cat said:

I'm looking forward to seeing the photos on Tuesday!

Sorry to disappoint but I've had to postpone the job to next weekend - some of the parts didn't arrive in time. At least it gives me a bit more time to prepare!

[Tonka]

On 21/08/2019 at 21:59, ivan&alice said:

I hope I don't disappoint!!

Ah, thank you for the recommendation but I have already placed my order with TW Marine. I am very pleased with their service so far and their silencers come with a recommendation, so let's see!

See should have gone to T Norris & Son

[jetzi]

8 minutes ago, Tonka said:

See should have gone to T Norris & Son

TW Marine delivered the complete order the next day, as promised. T Norris didn't answer my email (and still have not, four days later), or they may have had my business. I could have called but I prefer to deal in writing.

 

However the random ebay seller that I ordered two pieces of malleable iron pipe (which none of the marine engineers seem to stock) did not manage to honour their next day delivery promise, so I'm going to have to wait until next week for that.

 

TW Marine, unfortunately, did also not have a flange in stock. I had a good go with a Stilson today and I am quite convinced that the flange and the pipe connected to it is one contiguous block of rust. The nuts holding the flange to the engine however are easy to remove. So I'm ordering a new flange too.

[jetzi]

It was a hard, dirty and sometimes dangerous weekend of fun, but I have got my new silencer and exhaust system fitted. I'm not quite done, need to strap down things a bit better, lag the exhaust pipe, and clean up the tailpipe somehow - thinking of getting some 2mm thick steel, cutting a square with a hole for the exhaust, then bolting it over the whole lot).

 

As promised here are some pics of the job. First I cut out the old system. Then ground out the rust - turns out I didn't need to clean it, because taking the rust out removed the soot with it! Next I cut a larger hole for the silencer, with great difficulty. Fit a new exhaust flange and gasket, then screwed everything together with plenty of copaslip and a stilson wrench!

I achieved my goal of a hot shower at the end of a very dirty weekend, so although I definitely still have work to do here, I can at least run the engine.

 

I'm really pleased with the result, it's not quite as quiet as I'd hoped but if you're a boat away from me you wouldn't know that the engine is on. The exhaust itself is almost completely silent, the noise is coming from the engine itself. I plan to fit some soundproofing which will hopefully deal with that.

 

Thanks for all the support!

 

 

 

[WotEver]

That exhaust pipe is a bit long. 

 

Thought you'd appreciate my help...

[rusty69]

22 minutes ago, WotEver said:

That exhaust pipe is a bit long. 

 

Thought you'd appreciate my help...

Or the boat is too short. 

[WotEver]

2 minutes ago, rusty69 said:

Or the boat is too short. 

Good excuse to get it lengthened then. 

[Cheshire cat]

LOL. I had the same issue. The new silencer does it's job and now I get to listen to the engine valve gear!

[jetzi]

Regarding the builders galvanised strapping - I want to get this tomorrow, to fix down the silencer and reduce vibration. Something like this: https://www.screwfix.com/p/sabrefix-builders-band-galvanised-dx275-9-6m-x-20mm/38619

I'm planning on drilling a hole in the support above the silencer (that runs parallel to the silencer) to pass the strap through and support it.

 

How would I go about tightening the strap really tight? With cable ties they ratchet. Would I just pull on this as hard as I can and put a bolt though the holes? I feel like it's going to be hard to get the tightness I require...

 

 

[WotEver]

9 minutes ago, ivan&alice said:

How would I go about tightening the strap really tight?

If you created a cradle using the strapping, with the two ends joining at the top mounting point you could then put a long bolt through the two ends, a little lower down. As you tighten that bolt so the whole thing would tighten up. 

[Tacet]

It's only 20 gauge - so less than 1mm.  It's full of holes too with little land between.

 

So the problem will be the strap parting before it is satisfyingly tight.

[WotEver]

33 minutes ago, Tacet said:

It's only 20 gauge - so less than 1mm.  It's full of holes too with little land between.

 

So the problem will be the strap parting before it is satisfyingly tight.

You could always double it up.

 

I have about 9 metres of the stuff that I keep moving from shelf to shelf in the shed after I used a couple of feet off a roll a couple of years ago. At least it doesn’t rust

[jetzi]

I followed @WotEver's suggestion to tighten it with bolts and it's working a treat. I used long 8mm bolts necessitating a slightly larger hole than the strapping comes with but it seems to be plenty strong enough. Vibration is cut down to nothing and now I hear the swish of the water over the sound of the engine. I reckon a bit of sound insulation stuck to the underside of the deck and it will be just audible enough to count my revs! Very happy with the result and glad I decided to DIY it. Thanks for all the tips everyone, would have struggled to do it without you.