I’m having a rather serious problem with the yanmar 3GM that powers my Freedom 33.
Seawater is coming out of the air intake. About two liters have already come out.
I had taken photos before starting the renovation of the whole engine compartment but these photos were not explicit enough for the complete seawater circuit, when I made the new connections.
I had removed the whole circuit that allows hot water.
When I reinstalled the engine, I made a connection that may not have been the right one.
I estimated that the yanmar was above the waterline, but it’s probably not, in which case I’ll have to modify the circuit between the exhaust manifold and the mixing elbow.
This is not the same engine as mine but I’m a little confused by the narrative and pics.
You have seawater coming out of the air inlet? If this engine is like mine it means water is coming back through the engine? There is no way to “mis-connect” a seawater line into the air inlet box.
Typical way I know to get sea water into the engine is via the exhaust system after repeated cranking without a start. If all of that is correct, you have a pretty serious problem and should consider getting help.
If I am misunderstanding, then perhaps it is more simple. The picture you attached looks like the exhaust riser. This should have a smaller hose that injects cooling water into the exhaust stream. From there the water goes out with the exhaust gas. If you have somehow connected this line somewhere else it is possible, I guess, to get the problem you described. Like I said, this is not possible on my 4JH.
Not sure where the hot water comes in. In my set up, a plumbing problem would not end up with seawater out the air side.
As with most things, I always try to retrace my steps asking “what changed” and start my investigation there.
What I wanted to say is that I think the water coming in through the air intake is due to the fact that the pipe from the exhaust manifold to the mixing elbow does not go above the waterline and is not fitted with a vacuum valve. As shown in the sketch.
If I could see a photo of the installation on a Freedom with a yanmar 3GM and its original installation, it would allow me to confirm the validity of my hypothesis.
Now I am curious. I am configured per drawing so no water coming out the air intake (thank goodness) but the check valve at the top of the injection line is designed to allow air into the raw water circuit when the engine is turned off. This allows raw water to flow into the water box or back into the raw water circuit when the engine is turned off, Right?
If the check valve is not there and the loop is below waterline then water can fill the water box and flood the engine through the exhaust manifold?? Is that what can happen?
If so, I guess we should be checking the check valve from time to time.
I guess what you call the check valve is what is called vacuum valve on the drawing.
I don’t think the boat can fill with water with the engine off, otherwise it would have been the case for my Freedom.
After reinstalling the Yanmar 3GMD, I made a rough calculation of the water line inside the engine hold. I was quite wrong !
Here is a great article on the topic of Anti-Siphon valves. In the case of an engine coolant loops it breaks the siphon and prevents cooling raw water from filling the engine back into the exhaust elbow. Similar issue can occur with head.
“For the engine, the anti-siphon valve’s purpose is to stop raw cooling water from flowing into the exhaust manifold and through the exhaust ports in the block and then down into the cylinders when the engine is shut down.”
Thank you for this article which confirms what can happen
Here’s a photo (november 2009) of the engin compartment without the Yanmar.
In France, people use a wonderful expression:
“why make it simple when we can make it complicated ?”
Given the extent of the damage, I had to disassemble the injectors to see if seawater had entered them.
It turned out that injector 1 had water in it.
I cranked the engine to try to get the water out of the injector. Then I used the starter to speed up the process.
After lengthening the pipe leading from the exhaust manifold, adding an anti-siphon valve, and reinstalling the injectors, the engine restarted without a hitch.
What a relief !
