Wet Exhaust recommendations

[Peter]

I'm shopping for new exhaust components for the Vega (Yanmar 2GMF) and have decided to use a 2" Vetus Waterlock Muffler (because of it's small size) and a Vetus Air Vent in the raw water cooling line.

I'm looking for advice on a good exhuast hose ... something durable and flexible that needn't outlast the boat.

I'm also curious if it's a good idea to put in an exhaust thru hull with a flapper valve.

Any and all thoughts are welcome.

[Tim]

You don't have that many choices for exhaust hose. You need a heavy wall hose designed for use in wet exhaust systems. Most exhaust hoses are wire reinforced and/or corrugated to allow for the curves and bends required. For short, straight runs, one can choose a reinforced hose withoug the wire helix, but for sailboat exhaust you'll need the wire reinforcement.



Check out the Trident Marine site for some of the options.

Please buy the all 316 stainless solid band hose clamps like those made by AWAB for your exhaust system.

You don't usually see flapper valves on sailboats. They're designed more for flat powerboat transoms to prevent backflow when backing down. The flapper won't typically be rigid enough to work as a backflow preventer by itself. With the exhaust character of a waterlift system--periodic gushes of water with dry periods in between--I think a metal flapper would constantly bang the housing, which could be irritating, and a rubber one would be useless. Stick with an open outlet, and if you're concerned about backflow when some future offshore use comes into play, you can add an inline valve in the system somewhere inside the boat, which you could close when offshore in bad weather. Perhaps you have something specific in mind that operates differently than these?

You'll also need a high hose loop directly inside the transom, run as high as possible within the confines of the space.

A nice bronze outlet like this one might be a good choice, even mounted vertically in the Vega transom. The lip helps prevent drips from running down over the hull.

[Peter]

The clamps I am looking at are called "T-Bolt 316" .
OK, nix on the flapper, and wire-reinforced hose it is.

I like that simple bronze thru-hull. Mine is located low/center on the transom, but is too small for the 2" size of the replacement system. I'll use that nifty double hole saw trick to enlarge the outlet hole.

Going to get all the pieces together before I destroy the (still working, sort of) old system.

Will post some pics of the finished product.

[dasein668]

I second Tim's rec for the bronze exhaust flange. I have two on Dasein. They're grrrrrrrrrrr-eat!

[Tim]

The T-bolt clamps are a very good choice for exhaust systems as they provide even clamping pressure all around with no hard spots. The solid band clamps also do this, but the T-bolts have a wider strap, I believe.

[Peter]

Still fiddling with the exhaust system. Managed to remove all the old stuff today and was surprised how small the exhaust outlet is on the Yanmar 2GMF ... just over an inch.
That got me to wondering if I really need the 2" Waterlock and hoses. There's an awful lot of water in 12' of 2" hose.
What thoughts on downsizing to 1 5/8" Waterlock and hoses?

[Tim]

An inch? That seems really tiny. I don't think I've ever seen a diesel with smaller than 1-1/2" outlet, and most of the modern Yanmars are 2".

I went and stole the photo of your outlet from the other post. You're not by chance confusing the raw water injection hose (at the top) with the exhaust outlet, are you? The raw water injection hose is 1", but the exhaust outlet below it is clearly larger than 1". You may need a new bolt-on riser/elbow assembly to accept all hose rather than the rigid system you had, but that outlet (the rusting silver housing bolted to the engine) looks to be 1-1/2" to 2", as expected.

[Peter]

Sorry for being a bit vague ... it measures 1.32" coming out of the engine below the heat exchanger. The silver thingy is a butchered Yanmar piece mated to the old Albin outlet.

The whole works is history now and I'm making a clean start :)

But back to my earlier question: which would be a better system : 2" or
1 5/8"? My thoughts are the smaller system would be better matched to the engine. I've seen tests done on cars where a larger diameter exhaust degraded the engine's performance. I'm not sure if this applies to wet exhaust.

[Tim]

There's no need to use 2" hose and fittings if your exhaust outlet is only less than 1-1/2". I'd go with 1-1/2" for everything, given the diameter of your outlet, or whatever hose size best fits the outside diameter of your fitting.

The 2" suggestion was based on the assumption that your Yanmar would have 2" OD fittings in the exhaust. Since that's not the case, simply match what you have.

Good luck.

[Peter]

Good advice ... thanks Tim.
Boatworks magazine has an article on making a fibreglass muffler. A comment that caught my attention was that the muffler should have a capacity at least the same or greater than the capacity of all the rest of the exhaust hoses.

[Peter]

Still on exhaust systems:
I had a rubber boot over my exhuast outlet called a "Silent Sailor" (made in Canada, eh!)
I've never seen one of these before. I took it home and removed a handfull of barnacles and a dozen coats of paint to reveal this baby:

There isn't any info on the net, apart from a couple of message references. I understand it's purpose is to help muffle the exhuast.
Has anyone on the forum any info they can share?

Thanks!

[Tim]

You see those sorts of things on some older powerboats. The idea is that the exhaust exits below the waterline, muffling the sound. They do work rather effectively at that, but exhaust sound is much more of a concern with your old jacketed exhaust than it will be with your new system.

Because the waterlift exhaust combines the cooling water discharge with the exhaust gasses before exit, the sound is already substantially muffled, both by the baffles in the waterlift chamber and by the presence of water in the system. Therefore, all you hear, discounting any machinery noise, is a soft "whoosh" sound as the water exits the transom. There's no exhaust noise per se.

The old jacketed exhaust you are removing surely made a racket; I think jacketed exhausts sound terrible on sailboats, with a miserable cherry bomb-like sound. I'm sure the device you removed would have helped with that. Generally, you can hear the exhaust note of a jacketed exhaust for miles on a calm day; it carries far, and is distinctive, to say the least. One doesn't hear waterlift exhausts till the boat is very close--and then it's just the splashing sound of the discharge.

You can reinstall it if you like, though it will make little difference with the new system. To me, it just looks like one more invitation to marine growth, as you've already discovered.

[Peter]

I think the old Silent Sailor might be a good candidate for E-Bay ;-)

[Summersdawn]

Does the silent sailor help prevent the dark soot marks on the transom?

[Peter]

What soot marks??

Hey, I may just keep that thing on the shelf for a while and see if the new system leaves soot marks.

[Figment]

That pic of the Silent Sailor made my feet twitch.

The family boat in my childhood was a 25' Luhrs. It had a pair of such devices for the exhaust. Early in the season they make a fine foothold when climbing out of the water. Around late july they develop foot-shredding barnacles overnight. A lesson learned anew each summer.

They're great on a planing powerboat because they divert the exhaust (and noise) underwater at low speed, but once the boat planes off they're completely out of the water and all of that backpressure disappears and the engine breeeeeeeeathes so nicely.

Never seen one on a sailboat before.