Designing Wet Exhaust

[Lawrencemd]

I am designing a wet exhaust for the boat in the attached avatar. The engine will be a 250 inline chevrolet gas engine. I plan on running the rubber wet exhaust tubing from the manifold, injecting the sea water at some point, and exiting throught the side of the boat. Can anyone give me tips on how the hose should run,whether the outlet needs to be level with the manifold or higher or lower etc. I just want to ensure that no sea water enters the engine.

 

[juiceclark]

I'm no exhaust expert. However, this article was very helpful to me in designing a repower for my F-36 Trojan. It is very comprehensive. You may need to register on the site first (free) to get to it:
http://boatdiesel.com/Articles/Articles.cfm?P=20070601_Introduction.cfm

 

[kmorin]

Design Article

Lawrencemd,
Dave Gerr has a few articles at the Professional Boatbuilder Magazine, that are accessible online, covering almost every aspect of marine exhaust you're likely to find.

Dave is the head of Westlawn's (correspondence) marine design program and a practicing marine designer/engineer/architect @ Gerr Marine. His book the Nature of Boats available at Amazon, I'm sure, is also very informative about the basics of engine systems.

cheers,
kmorin

 

[SamSam]

Are you using a marine engine or an automotive engine?

 

[Lawrencemd]

My engine may have started as an an automotive engine but it was used in a fishing boat and is equipped with a water-cooled manifold.
Lawrence

 

[Capt Rhan]

Hi this is capt rhan
I have been messing with these things for my whole life and do know one thing. To keep the sea water out of the engine you will need A RISER in the system. I applaud your choise of power you won't go wrong with that one. Is it a 230ci or a 250ci ?

 

[Lt. Holden]

Hi Lawrence,
Check out Inboard Motor Installation from Glen-L Marine, very readable yet comprehensive. It covers several different styles and should prove helpful. Glen-L also carries a line of high quality pieces to put it together.

 

[KnottyBuoyz]

Maybe some of these will help.

 

[powerabout]

Whose manifold have you used?
or post a photo of it and I can suggest what to do next.

 

[Lawrencemd]

OK, we have decided what we are going to do. To start, heres the facts. The manifold exit is 2 inches higher than the exhaust port on the side of the boat. After doing some reading, I have learned that the highest point of the exhaust needs to be at least 12 inches higher than the exit at the side of the boat. So, using 90 degree black iron pipe, I'll run the exhaust straight up from the manifold at least 10 inches (manifold is already 2 inches higher), than 180 degree down with a port to inject the water (this will act as the riser), than a 90 degree sideways out to the side of the boat using rubber exhaust hose. What do you think?

 

[powerabout]

I'l still need to see that manifold as you might be able to buy those parts off the shelf to add height and then the water injection elbow?

 

[CDK]

I've used a waterlift muffler which I made from stainless steel, both input and output connected with exhaust hoses. Works like a charm: no exhaust noise and the engine can freely move in all directions. I've drilled a tiny hole in the bottom so the water can slowly drain away when the boat is not in use, but that was clogged up within a week.

 

[lazeyjack]

OK, we have decided what we are going to do. To start, heres the facts. The manifold exit is 2 inches higher than the exhaust port on the side of the boat. After doing some reading, I have learned that the highest point of the exhaust needs to be at least 12 inches higher than the exit at the side of the boat. So, using 90 degree black iron pipe, I'll run the exhaust straight up from the manifold at least 10 inches (manifold is already 2 inches higher), than 180 degree down with a port to inject the water (this will act as the riser), than a 90 degree sideways out to the side of the boat using rubber exhaust hose. What do you think?

hey buster Knotty gave you some help, so what did you do? ignore him