Exhaust siphon break

[jr438234606]

Hi all. I'm still trying to figure out this new-fangled Yanmar 4JH4AE. I'm working on the exhaust system and need to know where to install the siphon break. I'm thinking that these two large nuts are meant to be tapped into for just that purpose. If anyone has this engine, let me know if I am thinking correctly. My users manual doesn't identify the purpose of these nuts.

Thanks!

[brak]

I jave an older 4JH3E which looks just like this one. I am not sure there is a siphon break though. One of these nuts is tapped for water connection that is split in two - one part goes to dripless shaft seal, another into water muffler - not sure what the purpose of that is.

[jr438234606]

Originally Posted by brak

I jave an older 4JH3E which looks just like this one. I am not sure there is a siphon break though. One of these nuts is tapped for water connection that is split in two - one part goes to dripless shaft seal, another into water muffler - not sure what the purpose of that is.

Do you see a siphon break of any sort installed at you engine/exhaust?

[brak]

No, not that I know of. The way it is installed there is a short exhaust hose (downward) to the muffler, then another short downward run followed by 90 degree elbow and a long run of exhaust hose to the stern. At the stern there is an inverted U loop (metal) that goes above water line, then a kind of a rubber flapper valve(not sure, left over from previous engine) that connects to exhaust thruhull.

That's it - no siphon breaks as far as I can see.

[funsailthekeys]

Is the engine below the water line?

[funsailthekeys]

We have several Yanmars that have the break between the heat exchanger exhaust and the Exhaust riser elbow. Seems easy enough to just replace the short black hose with the break. Hope this helps.

[negrini]

Jr, mine was installed where water intake was cool, between engine water pump and heat exchanger, not at the exhaust, wich I think will have same breaker effect/protection. I believe the most concern has to do with your waterlock, as returning water from exhaust (when you turn engine off) could find its way back to the raiser elbow. Rule says you should move it up from the water level as much as rasonable (Volvo says 40 inch) and center it as much as possible (for when boat is heeling).

[Rockter]

If the motor is below the water line, it really must have a siphon break.
It really must.
They are not expensive.

It must go between the exhaust coolant entry point and the heat exchanger on this motor. On my olde raw water cooled motor, it is between the exhaust coolant entry point and the (wet) exhaust manifold.

[jr438234606]

Originally Posted by funsailthekeys

We have several Yanmars that have the break between the heat exchanger exhaust and the Exhaust riser elbow. Seems easy enough to just replace the short black hose with the break. Hope this helps.

Fun, the more I study it, the more I realize you are correct. The little short hose could easily be replaced with a length of hose with the siphon break at the top. I still don't know what the nuts/ports are for though...

[funsailthekeys]

There are several applications for the exhaust elbow so there are a few extra nuts and bolts. Yanmar being the wise entity they are try to use the same parts on as many versions of engine that they can.