I'm thinking I should install a vented loop on my yanmar 1gm, connecting the cooling water line to the exhaust elbow. But, I'm not sure about setup - anyone have pics of how they've done this on their boat? Mine is a CD25D. Many thanks.
-Alec
Yanmar 1gm vented loop?
Moderator: Jim Walsh
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Bruce Barber
- Posts: 53
- Joined: Feb 5th, '05, 15:27
- Location: 25D Nancy Dawson,
Shady Side, MD
Re: Yanmar 1gm vented loop?
I've done this by teeing into the thermostat-to-exhaust elbow hose and running a short piece of hose from there up to atmosphere, namely a vent (like a transom vent) in the cockpit just below the bridge deck. I was concerned at first that cooling water might be driven up that hose and spew out into the cockpit, but that hasn't been a problem. I haven't photographed it but will when I'm next to the boat.
Bruce Barber
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Steve Laume
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Re: Yanmar 1gm vented loop?
I think you guys are talking about two different vents.
The closed system part with anti freeze that Bruce is describing is usually handled with some sort of expansion tank, just like a automotive cooling system. The vent in the cockpit is an interesting solution. If the system ever does overheat then you will probably be getting a blast of scalding hot water into the cockpit and lose any coolant that is expelled. You are also running a non pressurized cooling system. Most radiator, or expansion tank caps create about 15 pounds of pressure in the system. This allows the fluid to run hotter without boiling. The open vent should probably be replaced with an expansion tank at a high point in the system.
I believe Alec was talking about the sea water side of the engine cooling and the concern that it would siphon back to the engine through the exhaust. This hose should have a high point with a vented loop in it. On Raven, this is located up under the bridge deck. This keeps it high and centered so it will be above sea level at any angle of heel.
I hope this clears up the basic differences, Steve.
The closed system part with anti freeze that Bruce is describing is usually handled with some sort of expansion tank, just like a automotive cooling system. The vent in the cockpit is an interesting solution. If the system ever does overheat then you will probably be getting a blast of scalding hot water into the cockpit and lose any coolant that is expelled. You are also running a non pressurized cooling system. Most radiator, or expansion tank caps create about 15 pounds of pressure in the system. This allows the fluid to run hotter without boiling. The open vent should probably be replaced with an expansion tank at a high point in the system.
I believe Alec was talking about the sea water side of the engine cooling and the concern that it would siphon back to the engine through the exhaust. This hose should have a high point with a vented loop in it. On Raven, this is located up under the bridge deck. This keeps it high and centered so it will be above sea level at any angle of heel.
I hope this clears up the basic differences, Steve.
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Bruce Barber
- Posts: 53
- Joined: Feb 5th, '05, 15:27
- Location: 25D Nancy Dawson,
Shady Side, MD
Re: Yanmar 1gm vented loop?
No, Steve. Same thing. What I've described is essentially a vented loop, but the "loop" part is the existing top hose in the cooling system and the "vent" part is the hose that ends in the cockpit. Since it's vented to atmosphere, there is no possibility of siphoning, which is the intent. The 1GM isn't FW-cooled and we're not talking about a closed loop. Sorry, no photos yet.
Bruce Barber
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Bruce Barber
- Posts: 53
- Joined: Feb 5th, '05, 15:27
- Location: 25D Nancy Dawson,
Shady Side, MD
Re: Yanmar 1gm vented loop?
Here are some photos of the siphon break.
The first is an overall shot looking aft, at counter level. (The big white horizontal band is the top of the opening into the engine compartment.) I've added a dotted line to show the route of the hose that runs from the tee, ending in the cockpit at the vent fitting shown in photo three. This hose runs between the liner and the deck/cockpit molding; therefore it's out of sight. The circle at the top end of the dotted line is a cover to hide the hole in the liner, which I had to cut to install the fitting.
The second photo is a closeup of the tee that's cut into the existing hose that runs from thermostat to exhaust elbow. It is the high point in the cooling system.
The last shows the vent fitting in the cockpit.
A "proper" siphon break such as you'd find at West Marine would be inside the boat and have a check valve to contain spray, but with the hose run up to cockpit level, cooling water never gets high enough to be a problem. And if it should, what's a few drops in the cockpit? Thus no valve. Calder discusses this in the second edition (and probably the first) of his book. (He also goes a step farther and suggests that a valve be installed in the exhaust line at the transom, but I doubt that many of us have gone that far.)
The first is an overall shot looking aft, at counter level. (The big white horizontal band is the top of the opening into the engine compartment.) I've added a dotted line to show the route of the hose that runs from the tee, ending in the cockpit at the vent fitting shown in photo three. This hose runs between the liner and the deck/cockpit molding; therefore it's out of sight. The circle at the top end of the dotted line is a cover to hide the hole in the liner, which I had to cut to install the fitting.
The second photo is a closeup of the tee that's cut into the existing hose that runs from thermostat to exhaust elbow. It is the high point in the cooling system.
The last shows the vent fitting in the cockpit.
A "proper" siphon break such as you'd find at West Marine would be inside the boat and have a check valve to contain spray, but with the hose run up to cockpit level, cooling water never gets high enough to be a problem. And if it should, what's a few drops in the cockpit? Thus no valve. Calder discusses this in the second edition (and probably the first) of his book. (He also goes a step farther and suggests that a valve be installed in the exhaust line at the transom, but I doubt that many of us have gone that far.)
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Bruce Barber
Re: Yanmar 1gm vented loop?
New diesel owner here so pardon my ignorance - curious what it is that you want to accomplish with this modification? I have a Yanmar 1GM in my 22D.
MHB Sailor