loop in exhaust hose?

[rrranch]

My ranger 29 has the water lift muffler sold here installed on it. After that the exhaust hose does a big loop up to the top of the cockpit seat and it also has a gate valve in it just before it goes out the transom. Our surveyor told me I have to remove the gate valve. I'm getting more irritated with him every time I read it. The valve works fine and is in good shape. I was wondering if I need it though and the loop also. I thought those were unnecessary with the water lift muffler. The water from the manifold is injected at the downstream side of the hot section after a big loop in it. It seems like redundancy. I do know the engine was flooded once and replaced. Maybe that's why they did all this. Under full power the exhaust exit is about 6 inches under water and I've rarely taken water over the stern from ship wakes. I need to replace the exhaust hose so how should I do it?

[Bold Rascal]

Hmmmm?

With your exhaust port 6" below the waterline then I would classify it as a "thru hull" and being such should definately have a valve on it. Incidently a gate valve is not really your best choice of valve type, should be a sea-cock.

It strikes me odd that your exhaust exits below the waterline. Maybe it's a common practice?

Have you considerred abandoning your below WL exit and installing an above the WL port? then you could forget the valve and your loop (as high as you can get it) would serve.

You'd still have that below WL opening to contend with.

I'm very curious to see what others advise..

[Marian Claire]

Is the exhaust port above the water line when you are not at WOT? Dan S/V Marian Claire

[TomG]

A picture would be worth a thousand words here.

I think gate valves are pretty much taboo in marine uses especially functioning as sea-cocks. I don't have a copy of the ABYC recommendations, but I'm pretty sure gate valves are not approved because of their chances of not fully seating (i.e. leaking).

I would think a valve that closed off the exhaust would be an odd design and potentially bad for the engine. I'm interested to see your exhaust setup.

Here is a great thread from our friend Maine Sail on thru-hulls and valves. After reading it, I think I'm going to go check on my boat!

Seacock Primer page

[Mo]

keep it as it is.

Keep it. If it works it works and it will keep the water out when the boat is heeled etc. The previous owner made sure it worked well...and apparently it does.

I have my hose coming out of the waterlift straight up to the cockpit floor, then it goes back and does a loop and out...it works. No valve in mine and it cant hurt to have it.

[hanleyclifford]

If your exhaust goes under water under power even 1/2" you should relocate the thru hull above, way above the WOT water line. Your engine does not like exhaling under water when it most needs to delivery the goods. You do not need any sort of valve at the transom but before the hose goes to the thru hull give it the maximum elevation possible to protect from a following sea. Gate valves are indeed a nono in the 21st century.

[Mo]

This make sense to you guys?

What Hanley said...I stand corrected...wasn't paying attention to the "gate" valve part.

[hanleyclifford]

Certainly the full loop does make it more difficult for water to get into the engine from a following sea, but if the engine is not running it is just about certain that a water trap will be established in the bottom of the circle. Can the cold engine start up and blow it's way thru that water? Dunno. My preference would be to take the waterlift discharge all the way up to the poop deck and then down sharply to the thru hull (relocated as high on the transom as one's aesthetic sensitivities will permit).

[Cellnav]

A valve isn't a bad idea between the exhaust exit and the riser. My exhaust riser came apart right shortly after I bought my well used C-27. The lack of a riser allowed water to flood in from the exhaust outlet in moderate seas and from the engine (if I continued to run it on a no-wind day). It flooded even more while under tow. I managed to plug the hole with a tee shirt but it sure got the wife excited to have 3" of water sloshing around the cabin sole until the bilge pump caught up. A valve would have made that scenario much easier to control.

Aloha,

Mike

[Mo]

Hanley, about 3 seconds after start up I hear the first splash and then it's steady as per my exhaust video I had posted on here one time.

You are right, there is always water in that muffler and the bottom of the loop....and one of the reasons I use auto antifreeze in the winter. Allot of fooling around to get it out when I can just prevent it from freezing.

I have allot of room under the cockpit to do this as others might be limited in what they can swing.

[hanleyclifford]

Thinking a little further on the loop...I can see that the water trap also offers some protection against damp, salty air while the engine is not running. This has to be considered, of course, in light of any additional back pressure imposed by the loop. Anyone have any back pressure data on this type of system?

[rrranch]

The outlet pipe on mine is about 4-5 inches above the water when I'm not moving. About 3 knots it's just getting submerged and at full power it's at least 6 inches under. I have noticed a couple times trouble starting it when we're still sailing or moving pretty fast. I bet the pipe was under water but I didn't check. potato in the tail pipe syndrome huh? It would make sense. Usually, if I have ran it at all in a day it starts immediately without the choke. Just not when I'm moving good still. That picture posted above looks almost exactly like my setup. Except for the valve.
I've gotten into the habit of closing the sea water inlet and taking the lid off the strainer so I can put a fresh water hose in it and running the engine for 10 minutes or so to purge out all the salt water. I have the t fitting too but this is a lot less messy and I don't have to worry about over pressuring anything. Is that a good idea too?

As for moving the exhaust outlet, I'm pretty sure I have the room to raise it up about a foot. Is that really a good idea? The transom isn't really that tall and it would put it into the boats name on there. Its still in it's original 1974 location though. I know some upgrades never hurt.

[Laker]

Ranch - what model sailboat are we discussing? Is your exhaust thru-hull underwater when the boat is at rest , or only underway?

[rrranch]

It's a 74 ranger 29. The through hull is well above water line at rest. It's only below at about half hull speed and above.

I was thinking about raising that through hull. Would that not make the loop ineffective as it would put the exit near the top of the loop. Just thinking outloud.

I didn't even know about the valve back there till we had the insurance survey done. I think the owner that put it in must have sent one of his kids below to close it. It's a tight squeeze getting to it. I can do it but I certainly wouldn't try it in heavy seas.

[ndutton]

Are y'all sure the exhaust location is a problem after 38 years in the factory configuration? Before going to the extreme of relocation maybe rrranch is a candidate for an exhaust backpressure gauge.

The readings may indicate a relocation is in order but then again maybe not. At least he'll have some solid information instead of wondering.

The inclusion of a valve in the exhaust line is to prevent following sea backflooding. The reason the valve is bad form is absentmindedness. If the engine starts with the valve closed you'll blow something apart. Catalina put a swing check valve in the 30 exhaust line, serves the same purpose but tends itself.