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Old 16-12-2008, 10:56   #1
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Perkin4236Change exhaust to new rubber system

We are purchasing a sailboat with a 1983 perkins 4236. The old steel pipe exhaust system is rusted through. Is it o k to put on the newer style rubber hose system?
With or without a muffler? I 've heard they can cause back pressure and the system, without a muffler, it should still be quiet?
Also the bolts that hold the exhaust pipe on the backside of the heat exchanger are going to be hard to remove. They will break off most likely.
Can I saw off the old steel pipe, leaving a 5 inch nipple and put the new rubber exhaust hose over the nipple that is left on the heat exchanger?
Then I would need to drill and tap to install the sea water inlet into the nipple.
Thanks for all your help
Indypopeye

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Old 16-12-2008, 11:35   #2
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I'm not an expert but it sounds like it'll work. The rubber hose exhaust only works for your system after the water injection but you know that already. You'll need an anti syphon in your injection system if your engine is below the waterline. It will be loud without some kind of muffler and backpressure is determine by restrictions and length of your exhaust system. Fiberglass mufflers or waterlifts are pretty easy to install. There are several good diagrams in books about exhaust systems. Nigel Calder mentions and draws them in Boatowner's Mechanical and Electrical Manual.
Kind regards,
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Old 16-12-2008, 12:15   #3
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Can you send some pics.
The "muffler" you speak about may be a water lock/lift, if so, you won’t want to delete it...it helps keep the water out of your engine.
The location where you mentioned drilling and taping the sea water inlet is pretty important, its been my experience that the nipple should inject the water around a sleeve inside the pipe that is closed up stream.

If the heat exchanger is in that bad of shape you may want to check out its integrity...also have a look at its zinc...it may look like a pencil inside and just a bolt head outside.

This is a critical area...get it wrong and you may be doing a rebuild...if you're lucky, a re-power if you're not.
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Old 16-12-2008, 13:34   #4
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I am afraid I don't have a picture of the engine space.
The boat is a Corintian 42 trimaran. So there is minimal heeling.
The old steel exhaust has a high loop, and where it starts down hill there is a saltwater inlet for cooling water. this is where the old system changes to rubber hose.
They are telling me the engine has 5000 hours.
I will have a good look at the heat exchanger.
This project will start at the first of the year.
Thanks for all comments
Indypopeye
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Old 17-12-2008, 06:19   #5
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If the exhaust that you are replacing is in the dry part of the system you cannot use rubber hose. It will burn. The reinforced rubber hose is wonderful stuff but can only be used after the water injection point.

Here is a link to a page that I hope will provide you with some guidance http://www.betamarinenc.com/exhaust%20systems08oct.pdf

A waterlift muffler is generally the lowest part of the exhaust system and is designed to act as the collector for all the water in the exhaust system when the engine is shut down. Back pressure is always a concern but if everything is sized correctly, you will be ok.

Good luck, Stanley
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Old 17-12-2008, 20:24   #6
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My Mentor told me to never-ever modify a factory installed exhaust system.....unless you are willing to be responsible for any subsequent engine damage.
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Old 17-12-2008, 23:56   #7
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That may be good advice on a boat thats still under warrenty...Having said that, I see lots of "factory installed" stuff thats pure rubbish...including exhausts!
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