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Old 05-05-2015, 18:23   #1
Registered User

Join Date: Apr 2013
Location: Anacortes
Boat: Red Admiral, 1979 Holman Pye 36
Posts: 71
Exhaust Check Valve

Hi All,

The time has come to replace the exhaust hose in the boat. Since it's a huge project it invites me to wonder if the system can be improved.

The system is less than ideal. The engine is almost in the middle of the boat and the exhaust hose has a long run aft. Along the way it goes through a Volvo in-line muffler.

There's no riser at the water injection point and the muffler is only at best a foot below the water injection. The slope of that section of hose isn't steep either so there's not much to discourage water from coming back up the hose.

I suspect this system may have been Ok with the original engine which probably had some extra height from the manifold down to the muffler. But now with the MD2030 it seems as if it wouldn't take much to have water slosh up into the manifold.

So I'm considering two possibilities. The one I will do if the parts will fit the other is intended as plan B.

If possible I'd like to put on a riser an then carve out some space below it for a water lift. Then I'd run the hose towards the transom and perhaps put in one of those Vetus gooseneck mufflers or maybe just a loop of hose.

But this system might not fit and I'd still like to do something to prevent water from sloshing up into the manifold in rough weather. Obviously that hasn't happened yet but it seems a wonder that it hasn't.

So my plan B is to stick with the in-line muffler but to add a check valve before that so water in the muffler and hose can't get back to the manifold.

I know you guys are the experts and I've read what I can but I have to ask directly what people's opinions are about the exhaust check valve. Anyone have experience with them?

I would think if they are that great then everyone would have one. There must be a down side but then the downside of ruining the engine is a big one and I sail and motor in some pretty rough weather so it seems prudent to address this ahead of time.

Thanks in advance, and of course there's nothing like the resource that is I really should contribute to help give back but don't do much of that sort of thing these days. Sure glad others do though. My expertise? Not really sure; I know lot about a little and a little about a lot.

korrigan is offline   Reply With Quote
Old 05-05-2015, 19:01   #2
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Join Date: Oct 2011
Posts: 2,501
Re: Exhaust Check Valve

Almost anything movable (ie. check valve) in an exhaust system will carbon up in short order, and no longer function. Worse yet, it will create an obstruction that will collect more carbon, and become a restriction in the system. I think your idea of a custom (higher) riser would be more reliable. Many center cockpit boats have reliable exhaust systems, so you might try to look at similar size boats to get an idea of how high to go. Best of luck. _____Grant.
gjordan is offline   Reply With Quote
Old 05-05-2015, 19:23   #3
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Join Date: Oct 2008
Boat: Custom cutter, 42'
Posts: 414
Re: Exhaust Check Valve

A check valve will work fine if it is external. Just like the exhaust flapper valves you see on semi trucks, but mounted on the exit of your exhaust at the transom. Fab it from 316 stainless.
Pauls is offline   Reply With Quote


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