Raw water Hydrolocked, again

[Captn_Dwt]

Hi Folks,

Well, it's happened again. The engine is flooded with sea water, and hydrolocked. It's happened before and I know what to do to fix the motor. No harm will be done there, I Hope. BUT....

What's causing this?
My boat is a 1980 36 dual cabin with a 2715e Ford-Lehman 120hp diesel.

1st occurrence that I'm aware of was last Fall when I went to view the boat for purchase. The vacume breaker on the raw-water line to the stuffing box had stuck, and the engine was locked and flooded.
That vac-breaker was a cheap unit...marlon with a rubber duck-bill..notorious for sticking.
It was replaced with a nice fail-safe unit by Beta Marine. It's a stainless elbow with a white plastic removable vent at the top. The vent looks like a small filter..

So this time, I go to start and she's locked tight. Check the oil...overfull by 2 qts at least. Pull the raw-water to exhaust elbow hose and out pours the water. Hmmm. Checked the vented loop...it's fine!

So, here we are:
What's causeing this flooding?

I'm hopeing that by comparing systems, we can isolate the problem. Here's what mine looks like:

From the last inline cooler (trani)..the raw water enters a 3/4 hose. In this hose is a "T" fitting, allowing a small, white 3/8 line to be split off and go back to the stuffing box. [This line does go to it's own vented loop, which also tests good] -- From the "T", the 3/4 line continues up to a Vented Loop, mounted by the back of the port fuel tank. The "top" of this vented loop is at the bottom of the cabin floor.
From the vented loop, the 3/4 line dips back down to the same level (of the trani cooler), and then bends up and attaches to the exhaust elbow for mixing.
The water-lift muffler sits on a wooden pad on the port hull, right behind the port fuel tank. That puts it pretty low in the hull.
The Engine Exh leaves the mixing elbow and bends over to the muffler. From the muffler, it's UP a few inches and then out the back.

Photos are now attached.
Does your system look like mine?
Is yours different? How so?


Now I have a theory:
When this happened the first time, we strongly believe that the vented loop did not vent. The seller found the duck-bill stuck together. That would allow siphone from the stuffing box into the engine.
This time, the vented loop was in good working order. But, I'm thinking it's not High enough. It's been 2 weeks since I ran the engine...just before Sandy came up the coast. During that time, she's been on the mooring, but she's been WAKED really badly. I found stuff scattered all over the cabin. The local lobsterman are running full-throttle up and down the river right now...and if the boat is broadside to the wake...it's a 30 degree heal back and forth.
So, what if, when she rolls to port, some water runs up the 3/4 line and over the top of the vented loop? For many repetitions, small amounts of water go to the Exhuast Elbow, and drain to the muffler. But...eventually, the muffler fills and the water begins to back up into the exhaust. The rest is history.
So, share your thoughts. Let's fix this, and make sure no one else has to have this happen.

[Updated at 6pm this evening].

[jleonard]

I do NOT have a vented loop or siphon breaker and have never hydrolocked. I have a standard elbow and the short (4 or 5 ft) exhaust hose goes into the waterlift muffler. That drops very little maybe 1 foot. The exit of the muffler is on top and rises to just under the floor and runs out the back at a slight angle.
If your cabin was as damaged as you say, then the boat most likely was stern high and allowed water to back into the engine via the exhaust elbow.
In my opinion the solution is to install a dry riser as high as you can make it after the exhaust manifold and before the wet elbow.

[Captn_Dwt]

Interesting...J...you are correct that the boat is more "stern-high" than usual because I've let the fresh water tanks get low. That would effectively change the drain angle for the main exhaust run and open the possibility for back-flow.
As you can see in the pictures, the rise after the muffler is not all that much....
Thanks for your thoughts.

[Captn_Dwt]

Mr. Leonard is most likely correct.
My exhaust runs about "flat" from the muffler to the transom. If there's a rise, it's only a few inches over the entire run. Also, there's a sag in the hose as is lays on the floor under the berth. Certainly, there's no 1/2" / ft of rise from the transom back towards the muffler, and there's no dry riser anywhere.

the attached pdf makes it pretty clear what was done wrong, either by the marina or the owner....whomever it was that replaced the entire exhaust system before I purchased the boat. And...where the heck was the marine surveyor ??? This is the second major missed fault. Ooof.

[jleonard]

Now that I can see your pics, I believe my exhaust takes a greater down hill from the engine to the muffler. Plus it appears that my riser out of the muffler is higher, but its hard to tell from the picture.

[jleonard]

Now that I can see your pics, I believe my exhaust takes a greater down hill from the engine to the muffler. Plus it appears that my riser out of the muffler is higher, but its hard to tell from the picture.

[Great White]

Hello,

Very interesting reading. I have had my 36 DC for two years now and after looking I do not have a siphon break on my stuffing box hose. No issues for me so far but is this something I should install??

Thanks in advance,
Ken

[Captn_Dwt]

Hi Ken,

I can't advise with certainty about the vent loop for the stuffing box hose. JLeonard states he does not have one either.
My boat's out for winter work now...no more testing on it until spring. By then, I will have re-worked the exhaust just after the muffler to build in a dry-rise of about 16"...and...corrected any low-spots in the hose-run back to the transom.
My personal evaluation for the need for a vented loop on the stuffing box hose would be this: disconnect that stuffing box hose at the "T" fitting, and find out what the "water line" position is relative to the engine's mixing elbow. You'll know right-off if it's a comfortable distance or not.

[rebuckley]

This may not be correct, but we did have an issue once when we decided that the muffler was nice, but decided to by pass. Like jloenard - we have no vent loops connected. Now I do believe the muffler (under our aft sleeper) has a flap in it that works like a check-valve and prevents water from flowing in via the exhaust - maybe your set up is allowing that reverse flow?

[Captn_Dwt]

The Fix.

Ok...so here's what I've done.
1) Re-work the Exh. hoses as they leave the mixing elbow. Instead of dropping down to a 90 and then over laterally to the muffler, I've used a flex connector at the elbow to connect the 90, and the hose now runs directly to the muffler. This eliminates a low spot in the system where water collects.
2) Re-work the Exh. hoses as they leave the muffler. Instead of simply staying at a single level and running a 90 to the exit in the bulkhead (see the last photo of my original muffler arrangement in the posts above), the run now exists the muffler and rises as high as possible, turns 90 to port, runs 12 inches along the bottom of the floor, turns 90 down and 90 aft to exit via the hose to the transom. (See the 2nd photo attached). This provides a "dry rise" in the system, as is common on sailboats, to ensure that healing will not cause water to back-flow to the muffler. The "rise" is only 9 inches...but that's 9 better than none.
On this boat, from the transom to the muffler top is all at about the same level.
3) There was a low spot in the long hose run under a small cabinet and under the bunk to the transom. This was caused by the hole being cut "low" in the aft wall of the closet / cabinet that is just ahead of the berth. There's a small door to access this cabinet (and usually the mattress is in the way) to open it. As usual, the floor is removable, and voiala...the exhaust hose passes here on it's way from the engine compartment to under the berth. I re-worked this hole, and otherwise made sure that the hose run is flat and level from the engine room bulkead to the exhause port on the transom. (no photos for this one).

The yard folks said that a dry-rise is not common to power boats....but there's no harm in having one. They also said that any low spots must be avoided; these will cause the hose to fail prematurely. Also, water held in a low spot can then be "tipped" forward when the boat heals...passing it's way along back to the muffler.

Finally, you'll notice that all clamps are t-bolt style. These are required fitting for commercial installations under USCG regulations...to I figured I'd just get ahead of the rules on that one.

So....is this something that eveyone should be concerned about?
My humble opinion is yes...in that the design of the exhaust system from the builder appears to be "flat", (no downhill run from the muffler to the transom as required by sound building prinicples), and that the circumstances can arise where such a system will pump water back to the motor.
Those circumstances appear to us to be:
1) A low spot in the exhaust hose run from the transom to the muffler, which will hold some water. This fault was built-in to my boat...I have no idea about others. The going opinion is that this fault contributed to the pumping action.
2) The boat needs to be unbalanced, tipping the transom up. [In my case, my fresh water tanks were about empty, and I have a generator installed. This set the resting fore-aft lay of the boat with it's transom high by at least 3-4 inches].
3) No dry-rise to stop the water from making it to the muffler, and a muffler that will eventuall fill and pass that water back to the engine.
4) Water conditions that rock the boat side to side, healing enough to dip the exhaust port under water, and then back up enough to encourage that water to travel backwards in the exhuast system.

Final judgement is up to you.

[Great White]

Captn Dwt.

Thanks for posting the info and photos. Im going to give my system and good check. My muffler lies horizontal under my aft berth and then out the transom so I will check for low points and any indication that it water could flow back to the motor. I am also going to install a vented loop in my stuffing box hose since when I disconnected it and lowered it 1 1/2" water started to flow out. Better safe than sorry. Looks like you did a great job.

Thanks,
Ken (Great White)

[Gilles philippin]

[/img]Hi everybody, i'm new to Albins, new to wet exhaust, (used to have a steel tug with dry exhaust) and i'm wondering if my system is correct....i got some pictures, the exhaust exits the ford lehman and drops, then goes about as high as the manifold as it enters the space under the bed, kinda goes strait to a vernalift and from that rises not much and gets to the stern. Does anyone see something bad? Please!
Thanks,
Gilles

[jleonard]

The problem I see is that you should be drinking better beer.
(only kidding of course)
I can't tell much by your pictures so I really cannot comment as to good or bad.
My muffler is located about where your batteries are. The inlet is a little lower than the exhaust elbow, and the outlet is high, just under the floor. Then it is a straight run of hose to the transom. The outlet fitting is maybe 2 inches above the water line.

[cdsailor]

Gilles,

First, I think you have to be careful when you start asking questions about boats that are approaching forty. In many cases, things that are less than ideal have worked fine and without issue for decades. So the question of "is it bad?" becomes a bit more complicated. Ultimately, you need to investigate and make that decision yourself.

That said, it appears that the 90-degree elbow just beneath the exhaust mixer is a low point, and the exhaust hose appears to travel uphill from there until it passes through the bulkhead. Ideally, the portion below the mixer that travels to port along the bulkhead would angle downward to the waterlift muffler (and the section from the muffler to the transom would also slope downhill). Once again, however, given that the boat is nearing forty without any issues (I presume) it just might be much ado about nothing, so only your estimation and experience can make the determination.

If you were to do your own investigation, a good first step might be to disconnect the exhaust hose from the mixer to see if and how much water is collecting in that first downstream elbow. If there's little to no water in there, you probably don't need to worry. If there's a significant amount of water in there, with the level only slightly lower than the exhaust elbow, you might answer your own question about the system's integrity.

Perhaps the biggest liability I see is that excessive engine cranking - without startup - could potentially pump enough water into that low spot to back fill the engine. That's a potential issue with all wet-exhaust systems, but more so, in my opinion, with your setup. As long as your engine starts normally and continues to pump exhaust gases through the hose, any water in that area will eventually be blown into the waterlift and out the transom.

And one more point: I see that your water injection hose loops up above the waterline to mitigate siphoning. Ensuring the integrity of that siphon break is important.

Anyway, hopefully this information helps you assess things. Keep us posted.

David

[RobS]

Sure does look like a potential big gulp of water sitting in the exhaust hose under the battery charger --- engine off in a rolling sea..... Because something has worked for a long should mean it will continue to work given the same working environment but put that into an unforeseen engine off pitch and roll situation and things could change...