Flooded the diesel last night

[phorvati]

I have ford lehman 90hp and I've ran it few years now. Small issue I had was that vented loop which is in the hanging locker always leaks while engine is running. So nice clothes get all moldy. Previous owner put a hose on top of the vented loop and ran it as high as possible, then looped it back down. But the thing still leaks salt water. So the reason why engine flooded is that i added a shutoff at that hose to prevent leak. Well I didn't realize that once i stopped the engine this would flood it. I'm still trying to figure out if it came from exhaust side, like water lift muffler drained back into the manifold, or it came through the intake raw water side. Like if I had shut off the raw water intake, would that prevent the flooding.
It was a long night but she is running again. Didn't look at the dipstick but I'll probably have to do 2-3 oil changes.
And with that shutoff on vented loop open, I ran the engine for about an 20mins this morning, after I shut it off it did not show signs of flooding. I.e it started right up 20 minutes later.

[tkeithlu]

Sorrry to hear it. Do check the crankcase oil for water (emulsion, looks like coffee with lots of creamer) right away - that's the place where you could do a lot of damage. Possibly the exhaust system cooling and air in it contracting sucked water, if your exhaust is underwater.

[Bill O]

If I had to take an educated guess, it came back through the exhaust side not the raw water intake.
Would change the crankcase oil and filter several times to remove any water from the engine.
Also if you can't stop the leak on top of the loop by cleaning the duckbill valve then replace either the duckbill if worn or the whole loop (top portion). Also remove the shutoff valve from the loop as this defeats the function of the anti-siphon loop.
So did the flooding occur while sailing and you were heeled over or upright when you shut down the engine? The only reason for this question is to determine if the loop is high enough above the waterline. Should check the height of the loop above the waterline. If the loop is in a closet, then heeled over to that side would lower it considerably compared to a center lined loop.
Technically, it is a good idea to shut off the raw water valve when sailing to prevent another possible source of engine flooding.


Bill O.

[phorvati]

Originally Posted by Bill O

If I had to take an educated guess, it came back through the exhaust side not the raw water intake.
Would change the crankcase oil and filter several times to remove any water from the engine.
Also if you can't stop the leak on top of the loop by cleaning the duckbill valve then replace either the duckbill if worn or the whole loop (top portion). Also remove the shutoff valve from the loop as this defeats the function of the anti-siphon loop.
So did the flooding occur while sailing and you were heeled over or upright when you shut down the engine? The only reason for this question is to determine if the loop is high enough above the waterline. Should check the height of the loop above the waterline. If the loop is in a closet, then heeled over to that side would lower it considerably compared to a center lined loop.
Technically, it is a good idea to shut off the raw water valve when sailing to prevent another possible source of engine flooding.


Bill O.

Changing oil is really easy on this boat. That's one plus. Lehman sp90 is 10qt Capacity. This is 4gal I guess the difference is salt water.

[phorvati]

I was at a dock. And the first time I ran the engine and shut it off with that vented loop leak valve closed, engine started flooding. I know this because 1.5h later I tried to start the engine and it was hydrolocked

[Sailmonkey]

If your exhaust outlet is above the water, the flooding occurred from the seawater inlet.

I’ll take a stab, that muffler is below the engine.

What has happened is that when you shut off the engine, the siphon break (that has been disabled) didn’t allow air into the seawater circuit to break the siphon. The weight of the water from the siphon break to the mixing elbow allowed more water to be pulled through the raw water pump and over the top of the siphon break, thereby filling the water lift muffler. This continues until water is pouring out of the engine intake.

Lesson....never disable a siphon break.

[phorvati]

So Bill, with respect to theory on exhaust side flooding vs intake side flooding,
Vented loop sits on the intake side of the mixing elbow. About 5 feet of 3/4" hose from elbow to high point under companion way. Which I am pretty sure is properly installed. At this point I am not visualizing how allowing air on the intake side, prevents water from comming back to the manifold from the exhaust side.
On the other hand, My waterlift is huge, and i have a fiberglass muffler as well. So i would say about 6gal of raw water is there at rutime. Wet exhaust is a 3" hose and there's probably 20 feet of it. Not sure what portion of it is water during runtime.

[phorvati]

Originally Posted by Sailmonkey

If your exhaust outlet is above the water, the flooding occurred from the seawater inlet.

I’ll take a stab, that muffler is below the engine.

What has happened is that when you shut off the engine, the siphon break (that has been disabled) didn’t allow air into the seawater circuit to break the siphon. The weight of the water from the siphon break to the mixing elbow allowed more water to be pulled through the raw water pump and over the top of the siphon break, thereby filling the water lift muffler. This continues until water is pouring out of the engine intake.

Lesson....never disable a siphon break.

Thanks, that seems to make sense. Yes muffler is 6 inches below mixing elbow. My lesson and I've had a westerbeake 40 before which I installed and rebuilt myslef and never had this issue, guess must have gotten lucky, is that I thought anti siphon is only for sailing in following seas and water comming back through exhaust. But I am realizing that you need to the hydrostatic or whatever it's called, analysis to see how gravity contributes to raw water flow while engine runs and afterwords, also while sailing and while in big seas.

[MicHughV]

Having faced similar issues in the past, I learned to close the seawater intake valve after shutting down the engine. Especially so on long offshore trips.
Off course this entailed a trip below to turn the intake valve handle, which fortunately was readily accessible...as I could bounce down below and have it off within seconds of shutting down the engine. When starting the engine, one must not forget to open the valve again first !!
One time, at night off course, the exhaust hose came off the muffler and the seawater instead of going overboard was going inside the hull. I kept wondering why I was hearing my bilge pump cycle on so many times.
Another time, the exhaust line clamps came off at the hull connection, causing another emergency drill.
If all that is not enough, the shaft coupler keeping the shaft on the engine came loose one time.
Another time the retainer bolt keeping the shaft on the coupler vibrated loose.
Even though these had all been wired to stop them from rotating, the wire eventually broke. I now use stainless steel clamps around each bolt. Seems to provide more security.
So now, I always run below to check on the engine while it is running. Every 30 minutes or so I will open the engine compartment for a quick peek to ensure all is well.
Finally, when offshore, I will close all the thru hull valves, except the engine and one toilet. This way, if I have a "sinking" problem I immediately know which valves to close.
Most engines live in some dark box with little light, so besides the water muffler issues it pays to check EVERYTHING !!

[Bill O]

Here is a good article on setting up an engine exhaust system. The anti-siphon between the exhaust manifold and elbow primarily stops the exhaust water from backing up. There is an additional riser in the stern (after the water lift muffler/muffler) to prevent flowing seas from flooding the engine.
Closing the raw water seacock prevents water from from being pushed in through the water pump and possibly flooding the engine. The forcing of water past the pump could be exacerbated if you have a forward facing strainer (speed scoop).


Bill O.

[Bill O]

This is even a better article for Guidelines for evaluating and installing wet exhausts


Bill O.

[billknny]

"Vented loops" that have a silly little one way rubber duckbill valve in the vent are the dumbest invention ever. They have two failure modes.

1. The silly little rubber check valve fails open, and salt water sprays all over your engine room, or where ever else it is mounted. This is somewhere between Bad and Very Bad depending on the location.
2. The dumb little rubber check valve clogs with salt, fails closed, and does not break vacuum. Engine syphons water back. Very, Very Bad.

These little check valves need to be replaced before they fail. Last I looked, the ones that fit in to the typical small antisyphon loops made by Forespar cost US$10.

The solution is simple. Remove the stupid little check valve, and connect a piece of tubing (1/4" is plenty big enough) that runs overboard. I run them to a place above the cockpit drain, that way the helmsman can see at a glance that raw water is flowing. Fool proof, and highly unlikely to fail. No need to remember to close valves or perform any other human interaction.

[mvmojo]

Originally Posted by billknny

"Vented loops" that have a silly little one way rubber duckbill valve in the vent are the dumbest invention ever. They have two failure modes.

1. The silly little rubber check valve fails open, and salt water sprays all over your engine room, or where ever else it is mounted. This is somewhere between Bad and Very Bad depending on the location.
2. The dumb little rubber check valve clogs with salt, fails closed, and does not break vacuum. Engine syphons water back. Very, Very Bad.

These little check valves need to be replaced before they fail. Last I looked, the ones that fit in to the typical small antisyphon loops made by Forespar cost US$10.

The solution is simple. Remove the stupid little check valve, and connect a piece of tubing (1/4" is plenty big enough) that runs overboard. I run them to a place above the cockpit drain, that way the helmsman can see at a glance that raw water is flowing. Fool proof, and highly unlikely to fail. No need to remember to close valves or perform any other human interaction.

These vented loop duckbills fail because they get salt water on them. Typically the salt will form crystals that prevent the valve from sealing completely. If the above solution (an overboard discharge - make sure there's no low loop in the line) isn't practical, another solution is to remove the duckbill valve from the vented loop and replace it with a piece of tubing with an interior diameter equal to the outside diameter of the duckbill valve fitting. Run this hose up a foot or two and then install an inline check valve in it. The air in the hose will compress when water is flowing through the exhaust and not allow water to reach the check valve, but when the engine is shut down, the suction will cause the check valve to open, preventing any water from flowing back into the exhaust and/or cylinders. This is detailed on yandina.com web site under projects. See Hints and Projects

[jamhass]

Ditto what billknny said.

In addition, the continuous piddle offers some nice diagnostic indicators. As bill said, you can see the raw water flowing. More flow than usual indicates plugging or fouling downstream of the vent, such as a restriction in the mixing elbow. Too little suggests issues upstream, like a fouled strainer, bad impeller, etc.

My volvo was plumbed this way and it is great.

[roverhi]

Listen and act on billknny and others advice. Flooded my Volvo twice when the anti-syphon failed. Ran the hose up as high as I could before exiting though the rubrail. Very little water pissed out with the high loop and never had a problem with engine flooding again. Keep changing oil till it's no longer milky. Two changes usually sufficed IIRC.