AQ130 exhausting through the water pump??

[louis.howe]

Hi All,

I have a Volvo AQ130 with a 270 outdrive.

Over the winter the engine has been struggling to lift water from the leg, and I have had to prime it using a hose directly into the filter. Once running it has been fine.

Today however it would not prime at all. So I though I would get a bucket of water and try and suck water from it directly off the water pump, thus cutting out the leg and water filter to rule out any blockages.

To my surprise I had exhaust gasses bubbling into the bucket with the engine running! It would not suck the water at all.

The impeller is tuning, but its a bit of a mystery to me?

Apart from this the engine is running well.

Does anyone have any ideas?

Thanks,
Louis

 

[am_dew]

Perhaps a clogged exhaust manifold?

 

[RicardoMarine]

Marine style exhaust manifolds incorporate a seawater mixing chamber within the elbow.
This is where the "spent" seawater enters and mixes with the exhaust gasses and eventually exit the system.


Each winter a pull my exhaust manifold drain port plugs as part of the winterizing process.
I also remove my seawater pump impellers as part of the winterizing process. (this extends their life)
I then do a short quick dry start to blow the exhaust out while doing my cylinder fogging.
During this, exhaust gasses from within the mixing chamber will exit all drain ports.
If I ran the engines fast enough, these gasses would exit via my open seawater pumps.
This is absolutely normal.


I'm going to suggest that if you are not achieving seawater pump pressure/volume, these exhaust gasses will have an easy access to this area, and that your seawater pump is probably faulty.

IOW, given the absense of seawater pressue, we could cause exhaust gasses to back flow into the seawater path on almost any marine engine.


Now... that having been said..... if for some reason this is NOT the case, then the only other thing that would make any sense, would be a tremdous obstruction within the exhaust system.
In which case the exhaust gass pressure would need to over-come the seawater pump's pressurizing ability.



.

 

[louis.howe]

This is encouraging, possibly the problem isn't as bad as I am thinking.

However, the exhaust gasses were entering with the engine on tickover. I may check the other engine to see if it does the same thing.

My guess was maybe the exhaust manifold has corroded inside, and it letting gasses into the water chambers?

Marine style exhaust manifolds incorporate a seawater mixing chamber within the elbow.
This is where the "spent" seawater enters and mixes with the exhaust gasses and eventually exit the system.


Each winter a pull my exhaust manifold drain port plugs as part of the winterizing process.
I also remove my seawater pump impellers as part of the winterizing process. (this extends their life)
I then do a short quick dry start to blow the exhaust out while doing my cylinder fogging.
During this, exhaust gasses from within the mixing chamber will exit all drain ports.
If I ran the engines fast enough, these gasses would exit via my open seawater pumps.
This is absolutely normal.


I'm going to suggest that if you are not achieving seawater pump pressure/volume, these exhaust gasses will have an easy access to this area, and that your seawater pump is probably faulty.

IOW, given the absense of seawater pressue, we could cause exhaust gasses to back flow into the seawater path on almost any marine engine.


Now... that having been said..... if for some reason this is NOT the case, then the only other thing that would make any sense, would be a tremdous obstruction within the exhaust system.
In which case the exhaust gass pressure would need to over-come the seawater pump's pressurizing ability.



.

 

[sandkicker]

Unless the exhaust outlet is blocked or badly obstructed, the water pressure from a properly running raw water pump will exceed exhaust manifold pressure ( typically just a couple of psi) and a corroded passage in the exhaust manifold will typically result in water entering the exhaust passages of the engine (and cylinder), usually to dramatic, if not catastrophic effect.