Exhaust Thru Hull

[ButchPetty]

I am considering changing my exhaust thru hull from the transom to a relocated position on the side of the hull.
Doing so I could eliminate 15 feet of hose that is rising most of the way and greatly relieve the back pressure.
My concerns of course is heeling with the engine running.
1. What kind of thru hull?
2. Flapper or not?
3. Angle of flapper?
etc. etc.

Does anyone have a side exhaust exit on there auxiliary and how does it work?
And any other concerns I made need to be aware of.

Note: Even on heel there is a loop that would be well above "real" water line. And the hose would run down from that loop to the exit point.

Thanks.

[ArtJ]

I have one on my Tartan 34C. It is just a inch or two above the waterline.
There is no flapper at least on outside. I believe that it is just a thru hull with nut and barb
for 1 1/2 hose. There is some sort of rubber bellows on the inside, don't
know the details beyond this. I am sure others will respond as well.
It has always been this way, and works fine.

Regards

[hanleyclifford]

Butch - The only real safe way to get away with such a modification is to install a full flow gate valve in the exhaust.

[ArtJ]

Hanley

What is a full flow gate valve?

Thanks

[hanleyclifford]

Art - Sorry, I took a little liberty with that term. The thought I meant to express is that the gate valve must be of sufficient nominal dimension that it not become the most restrictive component in the system. So in order to get the cross sectional flow area for a 2" it might be necessary to go up to perhaps a 3"NPT nominal gate valve. There may be other valve solutions that I'm not familiar with. Regards, Hanley

[ndutton]

My concern of course is heeling with the engine running.

Hanley,

Given that Butch is talking about motorsailing - engine running with the exhaust submerged on the lee side - I'm unclear over the intended benefit of a gate valve.

[hanleyclifford]

He will have to give up the motorsailing if he goes the side discharge route.

[ButchPetty]

No, I don't intent to purposefully go out and motor sail in a heeling situation like that, but that being said, you could still end up in a heel with no sails up and be motoring depending on conditions of course.
So yes, I want to know problems associated with this design in a "motor sailing/heeling" situation.
And thanks for all the input.

[ButchPetty]

I have one on my Tartan 34C. It is just a inch or two above the waterline.
There is no flapper at least on outside. I believe that it is just a thru hull with nut and barb
for 1 1/2 hose. There is some sort of rubber bellows on the inside, don't
know the details beyond this. I am sure others will respond as well.
It has always been this way, and works fine.

Regards

Thanks Art. Will dig into the Tartan design. Thats what I was looking for.
Cheers.

[ArtJ]

I motor sail with the exhaust a little underwater without a problem.
We had a discussion on this forum a while back about this. Don Moyer
said that it doesn't cause appreciable back pressure unless the exhaust
is more than a foot or two below the surface. There was also someone
on the forum ( I thought it was Neil?) who stated they made boats
for many years that had side exhausts.

[ButchPetty]

Thanx Art. I have already committed myself to the project. I'm sure if you have followed my post on this site you can see I also deal with a bilge motor. Plus's and minus's.
I think I am going to do the side thru hull so that it has a 2" id hose acceptance. I also want a brass vented scoop faced back wards. The loop that leads to that exit is always downhill even in a starboard tack. Plus, the fetcher that I didn't mention, their is a muffler of some sort that goes right at that thru hull. The football shaped thing that is at my transom now. It works so good. It will be incorporated because of its effectiveness of sound reduction and as a back flow preventer. Their is no water lift on my boat.

[ndutton]

There was also someone on the forum ( I thought it was Neil?) who stated they made boats for many years that had side exhausts

Without suggesting how you should make your side exhaust modification, here's how the Islander Freeport 41 side exhaust was configured and a brief description of the dynamics in practice:

• From the engine manifold exhaust port there is a conventional hot pipe section, minimum 12" rise.
• After the hot section rise, on the downhill side there is a raw water injection mixer.
• Continuing downhill is a conventional waterlift.
• The discharge from the waterlift proceeds up as high as possible, to the level of the deck.
• From the top of the loop the exhaust hose proceeds down to a conventional, open mushroom exhaust thruhull installed in the boot stripe.

Although there's a tendency to mount the thruhull higher than the bootstripe, the reason the Freeport thruhull was at the boot was there's no unsightly exhaust stain running down the hull and if running at the dock you won't be hosing down your slip neighbor.

The motorsailing backpressure concern was previously addressed on this forum HERE , post #8.
I'm not clear on your description of a "brass vented scoop." If you're trying to describe the exhaust thruhull configuration, it may have a negative impact the venturi effect described in the post. Can't say for sure because the "brass vented scoop" in unknown to me and my only experience is with a conventional mushroom thruhull.

No comment from here on trying to lift the discharge water without a waterlift. You're on your own with that one.

[tenders]

Before you get too far into this project I would suggest making sure you have the right clothing for it.

http://www.hulu.com/watch/10310/saturday-night-live-bad-idea-jeans

Perhaps Don should sell some of these on the site?

I've worn them for the following projects:

* "If gasoline won't start this engine, then ether will. I'll keep spraying ether into the carb until she catches!"
* "Hmm, the temp gauge is pegged at 230. Must be a broken gauge, I'll check it when we pull into the dock in an hour."
* "That odd, hot smell must be some other boat out here. Darn powerboaters!"

[Kelly]

Hmmmm...we seem to work on the same sort of projects.

[ButchPetty]

I have one on my Tartan 34C. It is just a inch or two above the waterline.
There is no flapper at least on outside. I believe that it is just a thru hull with nut and barb
for 1 1/2 hose. There is some sort of rubber bellows on the inside, don't
know the details beyond this. I am sure others will respond as well.
It has always been this way, and works fine.

Regards

Art, the hull of the Tartan 34C is so close to my hull design. My hull was also a take off of the Intrepid. The Tartan 34C's first hull was in 1968, mine is a 68 and also an S&S. And man, like my boat, the Tartan has some very beautiful lines. Very nice.