Exhaust transition 2" to 1 3/4" HELP?

[S/V Alchemy]

Originally Posted by timeout2

New 2" Centek waterlift muffler is $150 or so.

That's what I have. Works great in a somewhat unusual transverse exhaust set-up. Note the ball valve shut-off treatments. https://alchemy2009.blogspot.com/201...ng-part-2.html

[S/V Alchemy]

Originally Posted by Sailmonkey

The exhaust people (centek) make this.

2" X 1.75" Coupling - Centek Marine

I would suggest changing the water lift to 2" though. Especially if the original is old and made of stainless.

I would concur. Reducing back pressure is generally a good idea if you can pull it off, especially if you have a long exhaust run.

[Scrimshaw4]

I'd be concerned about the back pressure issue associated with the reduction. I'd recommend contacting the engine mfg to best understand why they have a 2" exhaust. I had a builder do what you're trying and it blew out the secondary muffler. They replaced everything with the proper size. Engine ran better and more efficiently. JMHO

[Qayaq]

Pull the inlet end cap off the muffler and weld in a 2" fitting, so the transition is in the muffler. I would definitely be doing a back pressure test on intial sea trials

[Scubaseas]

Weld a 2" pipe onto the outlet of the exhaust below the water injection point. You may not have enough room but you could take the exhaust manifold to a muffler shop and have them expand the pipe up to 2".



When it comes to diesel exhaust bigger is better.

[svJasmine]

I would not reduce the diameter from the engine. Make sure you don't choke it down.

[NorthCoastJoe]

I would never reduce exhaust size. If you are trying to save some money there are places like Blue Pelican in Alameda CA. I have seen several Centec 2" FG/plastic water lifts there cheap. They also has fittings and hose. https://bluepelicanmarine.com/

[Scubaseas]

OP wrote "Where is the best place to reduce the flow?"


I misread your intent. You do not want to reduce the size of the exhaust. If the engine is 2" you need 2" or bigger muffler and piping. 2.5" would be even better if it's a long run.

[georgeg305]

Re: 2" to 1 3/4" muffler transition.

Look up Centek reducers & couplers

They make FRP reducers of all size transitions.
George Goodall

[captlloyd]

Originally Posted by Scubaseas

Weld a 2" pipe onto the outlet of the exhaust below the water injection point. You may not have enough room but you could take the exhaust manifold to a muffler shop and have them expand the pipe up to 2".



When it comes to diesel exhaust bigger is better.

You have it right. I don’t understand the OP’s thinking. It’s like hooking up a garden hose to a fire hydrant. If you are enlarging to a 2” hose, any sort of necking down is going to defeat the purpose of the larger hose.

[Pete17C]

Looks easy enough to pull, take it to a machine shop and they should be able to swage it out 1/4"

[Pete17C]

Originally Posted by captlloyd

You have it right. I don’t understand the OP’s thinking. It’s like hooking up a garden hose to a fire hydrant. If you are enlarging to a 2” hose, any sort of necking down is going to defeat the purpose of the larger hose.

unless maybe you want more pressure ?

[captrick2011]

When I had the same problem I went with fiberglass reducers you can order them from most marine supplier