Wet Exhaust thoughts

Designs for inboard or outboard power

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CaptBob
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Re: Wet Exhaust thoughts

Post by CaptBob » Wed Jan 07, 2015 10:57 am

hoodman wrote:Is your motor maybe running a bit rich? Maybe you just need a carb adjustment or something.
I actually just bought a BRAND new Holley Carb a few months ago. The only thing that I adjusted though, was the idle. I didnt do anything with the fuel and air screws since they told me that they come pre adjusted. I guess though, you might have a good point.
I need to figure out which screw is which and maybe mess with those adjustments.
2000 Glen-L Double Eagle "Fan-Sea"

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CaptBob
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Re: Wet Exhaust thoughts

Post by CaptBob » Wed Jan 07, 2015 11:12 am

kens wrote:I cant help but wonder why your getting these fumes, and I an not.
I know you got a V8, but, I am not getting any fumes like that, none, notta, zip, zilch.
Both of us got a Double Eagle with exhaust exit close to centerline.
What can be so different?
You got me on that Ken. I have no clue, which is why I really want to tackle this.
Now with people cautioning me about back pressure, I'm starting to question making my exhaust going under water.
I highly doubt though that i will create THAT much back pressure but I may be wrong.
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Re: Wet Exhaust thoughts

Post by CaptBob » Wed Jan 07, 2015 11:26 am

Barra wrote:We used to do underwater exhausts on ferries and yachts, but always fitted a bypass above waterline for when the vessel wasn't moving due to back pressure issues.

We mainly did it for noise and aesthetic reasons not for fumes and it was on larger vessels (120ft - 300ft).

They are tricky do do correctly (one company I worked for wouldn't go near them) so if you've got other options I would start there...
My engine sits well above the water line, plus my risers are 4" and my exhaust tubes run back at an angle for about 8' to the transom, so that is why I don't think that I would really have siphon issues.
most of my boating is around the harbor, and rarely do I ever go on plane and back down on the throttle repeatedly.
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kens
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Re: Wet Exhaust thoughts

Post by kens » Wed Jan 07, 2015 12:40 pm

Sounds like you are aggregating several issues that are beginning to all add up.
You say you are running slow, low RPM, low speed, and now exhaust fumes issues.
With a V8 in a Double Eagle, you should get up on plane and Fly!!!!
Im getting up on plane with a 4-banger.
I can't help but think there is something NQR in your engine.

Is your fuel consumption running very much high??
Fuel consumption may be your tell-tale sign.
If you got high fuel usage and low speed, then you got your proof.

Ken
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

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CaptBob
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Re: Wet Exhaust thoughts

Post by CaptBob » Wed Jan 07, 2015 12:52 pm

Well, based on your advice about adding the spray rails to fix my speed/listing issues, I think I will be ok once that is all completed.
I have not had the time to actually do that, since I had to complete a couple other more pressing issues. (Repacking, new risers, draining starboard fuel tank.....and so on).
So now that the fumes from my exhaust have been an issue, I would like to tackle that next.
my engine seems to be running fine at the moment with no apparent issues.
Fuel consumption also doesn't seem to be out of the norm as well.
2000 Glen-L Double Eagle "Fan-Sea"

SunFun
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Re: Wet Exhaust thoughts

Post by SunFun » Wed Jan 07, 2015 5:06 pm

"Wet Exahaust" pipes are used all the time on "Go Fast" boats, but usually to avoid noise tickets 8) .
Although I'm lucky and my pipes are at the water level, a few of my boating buddies have had to get creative to pass the noise laws.
Some are low enough to exit under water at all times, others only worry about being quiet while at idle in no wake zones.

Some have made impressive SST pipes but many use 3" or 4" rubber drain fittings from Home Depot.

As for the siphon issue, most haven't worried about it, but a couple have drilled small holes at the top of the pipe to break any siphon.

Google "Boat Exhaust Turndowns" and you will see many examples.
You can also ask at any performance boat dealer and they will be able to give you some ides.

Good Luck, Scott

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Re: Wet Exhaust thoughts

Post by CaptBob » Wed Jan 07, 2015 7:26 pm

Thanks Scott!
You are the second person that has mentioned making sure there is a hole at the top of the elbow to break any kind of siphon.
I'll keep you all posted as I make this correction.
Also, a local mechanic mentioned that If the pipes are facing down under water, that the chances of water being shoved back while the motor is running are extremely low. He said it's more of an issue if they are straight pipes with no flap and also worse if the engine is not running.
2000 Glen-L Double Eagle "Fan-Sea"

Trackhappy
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Re: Wet Exhaust thoughts

Post by Trackhappy » Wed Jan 07, 2015 7:54 pm

How about initially just add a 45 degree elbow to point them outboard and see if it helps. Just clamp on some PVC elbows for a test run. The issue is not noise here, but fumes and forcing the stream outboard my be enough to cure it.
By the time I have built a boat, I'll be ready to build a boat....

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Re: Wet Exhaust thoughts

Post by CaptBob » Wed Jan 07, 2015 8:01 pm

You can see here why I need to "shove" a pipe in to my existing exhaust pipe and have them welded to stay in place. I don't have any excess pipe to clamp around.
Also, the white scum line is about an inch before the top of the pipe. So maybe a 45 degree elbow may be enough.
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kens
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Re: Wet Exhaust thoughts

Post by kens » Thu Jan 08, 2015 4:20 am

what size pipe is your exhaust run?
that looks real small in the photo
what size I.D.?
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

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Re: Wet Exhaust thoughts

Post by CaptBob » Thu Jan 08, 2015 10:03 am

ID after the muffler and thru transom is 2".
2000 Glen-L Double Eagle "Fan-Sea"

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kens
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Re: Wet Exhaust thoughts

Post by kens » Thu Jan 08, 2015 4:10 pm

Gosh that seems small, even my 4 banger has 3" exhaust. All V8s that I know of run 3" minimum is your manifold elbow 3"?
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

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Re: Wet Exhaust thoughts

Post by CaptBob » Thu Jan 08, 2015 4:25 pm

Its 3 1/2" ID
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Trackhappy
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Re: Wet Exhaust thoughts

Post by Trackhappy » Thu Jan 08, 2015 4:52 pm

You are gonna have to come up with some kind of flange that will attach using the existing holes. Maybe get your local exhaust place (one that works in stainless) to fabricate an elbow with a flange for you. If you are capable, you can get some 316 and cut them out and just get the shop to weld them up for you.
Alternatively PVC flanges something like this:
http://www.stormplastics.com.au/flanges_adaptors.html

An make it up in plastic to test it out.
By the time I have built a boat, I'll be ready to build a boat....

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Re: Wet Exhaust thoughts

Post by CaptBob » Thu Jan 08, 2015 4:57 pm

I was thinking of making a mock up as well out of plastic, to first test it out and see if it eliminates the fumes.
Then, if that worked, I would have a SST elbow made.
The way I was thinking of having the SST attach, is fitting the elbow in to the existing pipe, then have is welded around to the outside to stay in place.
2000 Glen-L Double Eagle "Fan-Sea"

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