Bad manifold, perhaps?

[TomG]

I know you all are growing weary of my troubles, but I ask your indulgence once again as I query the knowledge-bank here.

You all are painfully aware of my "PCV valve/water in the fuel" issue I've been having, that I had believed was solved. Until today.

I had the opportunity to check on my solutions today and I am disappointed to report that my problems have returned.

Symptoms: After running beautifully a few days ago, today the engine wouldn't start. Pulled a plug and it was wet with water. Not a lot, just beaded up. Cylinders look fine (not flooded). All the plugs look about the same. Maybe 3 and 4 look a little wetter. I drained the carb fuel bowl and it was full of water. Racor water separator was clear. Pulled the flame arrestor and the carb throat was full of water/gas.

I had to get back to house, so I didn't do a compression check, but I did one last week with the same symptoms and all the cylinders were good (each one was 95 psi). Assuming the next compresson check is normal, would the manifold be the likely culprit here? Or maybe the manifold gasket?

My plan is to remove the manifold and pressure check for leaks or cracks. Is this a logical plan? I can't think what else it could be... I am puzzled how water can move from the carb throat to the fuel bowl, though.

Thanks for reading!

[JOHN COOKSON]

Tom

Sorry to hear of your continuing problems.

I think you can pressure test the manifold without removing it from the engine. Experts will be along soon to confirm or shoot this down.

Are you certain you are not getting water back up from the exhaust system?

Boat engines remind me of personal relations. When they are good their great. When they are bad they are ..........really bad.

Chin up.

TRUE GRIT

[TomG]

John, I'm sorry to keep bothering you guys... I feel like I should let someone else have a turn.

I don't think it's water backing up from the exhaust. I have the standpipe exhaust system, so there is very little that can back up into the manifold. Also, this is a new problem (I think!)

Planning on testing the manifold tomorrow. I'm just wondering if I'm missing something more obvious.

I'm disappointed only in that I've missed some great sailing opportunities. I'm sure with an endless supply of money and labor, I'll get this figured out.

[ndutton]

I agree the manifold should be tested but one thing struck me in your success story on the PCV thread. You said you thought the water from a prior problem had been held in the filter only to leach out after cleaning things up. That seemed like a stretch to me. Changing the filter would confirm or debunk the theory.

I know you said the fuel from the tank was water free but I keep going back there. As events unfold, don't forget the outboard tank test. It will provide a wealth of information. You could even try it before testing the manifold. If water returns with the outboard tank test you are pointed toward the manifold. If not, besides clearing the manifold as a source . . . . we're looking at the on board tank again.

Now, how can I blame all this on an adjustable regulator??

edit:
An internal leak in the standpipe will deliver water straight into the manifold and plenty of it. Any steam out the exhaust thru-hull?

[TomG]

Neil, that's a great idea! I'll try that first thing tomorrow. I can't get any water out of the fuel tank and I can't find any in the water/fuel separator, but running the tank test would confirm that.

Having had the occasion to disassemble the carb several times, I still find it hard to believe that this much water could find its way into the fuel bowl side of the carb from the throat side. Seems to defy physics. My theory is either the manifold has a leak or the head gasket has a leak and the water is draining back down the intake manifold into the carb. If it's the manifold, that would explain why the plugs get wet, but the cylinders don't fill with water. It's just water being drawn in through the intake that keeps fouling things up. It would also explain why I can't find water in the fuel system.

I'll check the fuel, the compression, and the manifold pressure tomorrow. I hopeful that will lead to some clarity.

[ndutton]

You said two things that to me contradict each other. First,

I still find it hard to believe that this much water could find its way into the fuel bowl side of the carb from the throat side. Seems to defy physics.

then

My theory is either the manifold has a leak or the head gasket has a leak and the water is draining back down the intake manifold into the carb.

Any water incursion by way of the manifold either by breach or back through the exhaust would enter the carb into the throat, no other way.

The only direct path into the carb bowl I can think of is via the fuel delivery system (tank, pump, filter). So if incursion via the throat is unbelievable (I didn't say impossible because I'm not absolutely certain), what's left?

[smosher]

My exhaust pipe broke which didn't push the water out and it backed up into the cylinders, the throat, everywhere.

Steve

[ndutton]

What about the carb bowl Steve? Any water find its way in there?

[smosher]

Yup, filled and it was turned into jello

[ndutton]

Well then, that supports Tom's manifold theory. We'll see what he comes up with.

[TomG]

You said two things that to me contradict each other. Any water incursion by way of the manifold either by breach or back through the exhaust would enter the carb into the throat, no other way.

The only direct path into the carb bowl I can think of is via the fuel delivery system (tank, pump, filter). So if incursion via the throat is unbelievable (I didn't say impossible because I'm not absolutely certain), what's left?

This is sort of my point. With my rudimentary knowledge of the A-4 and the Zenith carburetor, it seems to me that it would be very odd for water to enter the fuel bowl from the throat. I suppose it could enter via the main jet and as the water is heavier, would continue to suck water in through the main jet at idle (the idle ports being higher in the system and bringing fuel off the top of the bowl rather than the bottom could conceivably continue to supply the engine with fuel until the fuel bowl was full of water). I bring it up because I simply do not know if it is possible or not.

What I know for certain is this: water is in the throat of the carb and in the fuel bowl. I can't find a drop of water in either the tank or the Racor fuel/water separator, the pump, or the in-line polishing filter. I doubt the exhaust system is culpable, as I have a standpipe. It seems to me that the only way for water to get in the fuel bowl is through the fuel inlet, but I'm having a very hard time reconciling the facts, as they themsleves are contradictory.

[ndutton]

Tom,

Steve has first hand experience of water entering the float bowl via the throat so all theories are still on the table.

[TomG]

edit:
An internal leak in the standpipe will deliver water straight into the manifold and plenty of it. Any steam out the exhaust thru-hull?

Now that's something else to consider. The standpipe is new and it's a heavy duty real deal, but I will keep that in mind. Thanks for the suggestion!

[Dave Neptune]

First thought

Tom, it's looking more and more like your manifold is comprimised or possibly still a gasket. If the manifold has a hole in it and it is in the front half the water after stopping the engine could dribble down the carb on the air bleed side and fill the bowl after shutting down. If the water were a back syphon at least one of the cylinders would have to be full of water~don't ask of my experience here.
If the Racor or water saparator is free of water it has to be coming in from another direction altogether .

Dave Neptune

[Carl-T705]

I thought you mentioned in another post your A4 was FWC. If it is it should be flooding the engine with coolant (AF) not water, correct? Or when you say water you mean coolant. Flooding with coolant /antifreeze could be a headgasket, block, manifold problem, flooding with water would be an exhaust plumbing problem. I doubt you could have that much water in the fuel system and flood the engine up to the tops of the pistons, it would run out the spark arrester first.