Engine Siphone Break

[engdude62]

I just replaced the mixing elbow, joint and exhast manifold extension on my 2GM20F and was told by the local Yanmar dealer that I should have a Siphone break installed between the mixing elbow and the heat exchanger or I could flood the engine with sea water. Currently I have a preformed short section of hose connecting the heat exchanger to the mixing elbow fitting as is shown in the Yanmar parts catalog for this engine.

Can any S2 9.2c owners shed some light on this subject?

A quick observation of my installation lends me to think that what I have is a factory original installation. Taking a line of site view from my mixing elbow fitting accross the engine room to the Starboard thru hull fitting for the bildge pump it looks like the mixing elbow fitting is a good 2-4 inches higher than the thru hull fitting which is another good 2-4 inches above the waterline. By my calculations I would say the mixing elbow fitting is 4-8 inches above the waterline.

I wouldn't mind installing one of these items as a safety measure however I don't want to add something extra to the system that my cause future problems if it's not really needed.

 

[Calypso]

I don't have one.

 

[engdude62]

Do you currently have your boat on the market? I saw a boat online located in NJ that looks like yours and I believe it had the 3GM engine installed. I guess the 3GM intallation should be similar to the 2GM installation within this model boat.

So your mixing elbow is also plumbed directly off your heat exchanger like mine? I think that must have been the S2 factory installation method.

The boat I just bought in Miami actually came from and spent most of it's life up in NJ before being moved to Florida about 2-3 years ago. From her records I believe the name of the boat while up in NJ was "Silhouette"

 

[woodster]

I just replaced the mixing elbow, joint and exhast manifold extension on my 2GM20F and was told by the local Yanmar dealer that I should have a Siphone break installed between the mixing elbow and the heat exchanger or I could flood the engine with sea water. Currently I have a preformed short section of hose connecting the heat exchanger to the mixing elbow fitting as is shown in the Yanmar parts catalog for this engine.

Can any S2 9.2c owners shed some light on this subject?

A quick observation of my installation lends me to think that what I have is a factory original installation. Taking a line of site view from my mixing elbow fitting accross the engine room to the Starboard thru hull fitting for the bildge pump it looks like the mixing elbow fitting is a good 2-4 inches higher than the thru hull fitting which is another good 2-4 inches above the waterline. By my calculations I would say the mixing elbow fitting is 4-8 inches above the waterline.

I wouldn't mind installing one of these items as a safety measure however I don't want to add something extra to the system that my cause future problems if it's not really needed.

you can get the anti syphon loop from scot marine produsts in fl ...it goes on the sea water outlet at the rear of the heat exchanger ...and the other end goes on the sea water pipe on the mixing elbow ....set it as high as you can ....... hope this helps....as far as i know it is an after market item.....
i dont think SBO has them for sale.......

regards

woody

 

[Calypso]

Not listed for sale. I have seen the one you speak of. High asking price.

 

[BobM]

i believe that vetus makes one too that is reasonably priced.

 

[Maine Sail]

Not listed for sale. I have seen the one you speak of. High asking price.

You get what you pay for... The Scot Pump siphon break is the most relaible siphon break I have come across.

Also you can build your own "loop" and plumb the "breaker" to it..

Not having a siphon break is kind of like going to Vegas. You may get lucky for a while, but you'll eventually lose. Once a siphon is started it can continue after the engine is shut down.

I siphon out our spa about 6 times per year to change the water in it. The high point is about a 5' lift from the bottom of the tub and about 2' above the high point of the water before it gets out to the driveway heading for the street drains. The low point of the hose however is lower so the siphon continues to work once started.

RW pumps are not positive shut off devices and as the pump body wears or you lose an impeller vane the "flow reducing/stopping" ability greatly diminishes until you eventually fill a cylinder with water and the starter just goes "click, click"..

 

[BobM]

interesting read from Don Moyer

http://www.moyermarine.com/forums/showthread.php?t=2922

 

[Maine Sail]

http://www.moyermarine.com/forums/showthread.php?t=2922

Siphon breaks sucking air is common in many incorrect head and engine installations. These devices break or allow air into the system on vacuum, as when the engine is shut down, and close on pressure. This is why they should not be inserted between the inlet seacock and the RW pump. They should be installed on the "pressure" side of the RW pump not on the suction side. Same goes for head intakes..