QSM11 exhaust mixer elbow

[Greg]

So I sucked up some sand / small pebbles / seaweed etc. The strainer filled up and now my starboard engine has a cooling issue. It is fine up to about 1200RPM's then it starts to climb above 165. It never goes above 162.

I back flushed the engine from the gear cooler to the intake, checked the intake grate, impeller, etc. but it all looked good.
I even got a small piece of an impeller from a previous failure.

I am wondering if some debris may have plugged the exhaust elbow.

How hard is it to remove the elbow and what does everyone think the odds are that it is occluded?

I checked the 'firmness' of the hose from the cooler to the elbow, thinking if the elbow was plugged the hose would be firmer. But it feels the same as the port. I did this at 1200 RPM's. The stainless pipes also felt about the same temp. Although I think maybe a bit hotter than I remember.

 

[cod]

Greg,I would suguest removing the upper stainless steel pipe that is connected to the after cooler and see if you have any debris at that point. I believe it would collect there before making its way to the exhaust elbow

 

[cod]

View attachment 25292

Greg,
I took this photo last falll when I was sevicing the Aftercooler. This is the inlet side(top) of the aftercooler. You can see all the impeller pieces that I needed to pick out. Amazingly, I was not overheating. More importantly, you can see the small ports that the water flows through and this is the first stop after the water pump. I don't think backflushing will always do the trick. Also check the fuel cooler.....

 

[Greg]

Steve,

Thanks. That is a good idea. I was hoping that the sea strainer would have caught everything but apparently not. Can you get to most of the input side of the after cooler with just a pair of tweezers or something?

I am wondering about the size difference in the fuel cooler tubes and the aftercooler. It would have to clear through the fuel cooler first.

The reason I was thinking exhaust elbow is because I descaled my engines a couple seasons ago, but never did anything with the elbows. I thought I have heard about others that have had issues with the little holes getting clogged.

When I backflushed I used two garden hoses (from two different faucets) into the input of a pump, then to the rubber hose that normally connects to the elbow. I removed the impeller and capped the shaft seal cooler line, then turned the water and pump on.

We have really good water pressure at the marina, but when I turned the pump on and went to open another hose bib in a different slip, there was barely any water coming out of it. So I know there was really good flow through the engine. Then, while the pump was running, I opened and closed the seacock several times. The pressure would build up in the engine (you could hear the pump strain) then I would quickly open the seacock and you could hear the water rush out quickly.

I am going down tonight to take a look, I have extra o-rings for the stainless pipe so I'll take a look.

 

[cod]

Greg,

Tweezers, small needle noose pliers, or if you have the fishermens needle noose that are bent at a right angle, they may work best.

Good question regarding the tube size of the fuel cooler and the after cooler. Unfortunately, I don't have an answer, so its going to be a process of elimation approach...... Good luck and keep me posted on what you find

 

[Greg]

So I checked the inlet to the aftercooler and it looked pretty good. I did recover three small impeller pieces from the past. The pic below is before recovery, they were hiding down in there.

So this was not a location of a blockage. I then pulled the exhaust apart to have a look at the elbow.

That looked OK also.

So I guess next on my list of things to check is the fuel cooler. I am really not expecting to find anything there either, I got really good flow while backflushing. The fuel cooler looks like quite a project to get at as well. I think I may just get a borescope and take a peek through the zinc hole.

Assuming I don't find anything there, what's next? I doubt there is anything caught in the coolant heat exchanger. The impeller is like brand new, the cams inside the water pump seem ok, but I have never changed them.

This problem started from starting the engines while we were essentially on the bottom and sucking up seaweed, sand, small gravel. Could something else have happened, other than clogging up the sea water circuit?

Is there some way to check the flow? maybe pull the line from the transcooler and time how long to pump x gallons? Compare it to the other side. How bad would it be to run with no water in the exhaust for 30 seconds or so? The problem I see is that it runs cool at low loads/RPM's, so the flow may be fine at idle.

 

[Alex F]

Greg,

I can't help you pointing where the blockage is, but it sounds like your boat doesn't have Barnegat or Great South Bay sea strainers: http://www.discountmarinesupplies.com/product.cgi?group=71488&product=83205

These things make night and day difference when it comes to eelgrass or seagrass.

However, I'd say that your problem was the mud that got sucked in and is still hiding somewhere. If this issue took place in your marina, then I think you need to find much better long term solution, b/c it's the 2nd time you got this type of problem due to low water in there. It might be a sign to relocate. I don't think that bow in will be the solution as your fairway is too shallow, if I recall.

 

[Greg]

Alex,

Those intakes look pretty nice. This didn't happen in my marina, we were anchored out in Manhasset Bay. I didn't realize there was like a 10 foot tidal range. When I saw it was getting shallow I started the engines to move, but it was too late, I sucked up some junk.

It's odd though, everything I open looks clean, I get good flow on the backflush. But there must be something in there somewhere. It was mosly sand/small gravel and seaweed.

I can now only travel at displacement speeds. At least I'm saving money in fuel.

 

[Alex F]

Wow, that's some wake up call for all of us going to new waters. We have only 2' of tide swing, so I can see how easy is to overlook unexpected switch in tide swing.

I would suggest don't waste too much time and call Cummins tech over.

 

[cod]

Hey Greg,

Any developments on this issue?

 

[Greg]

Not Yet. I just got a 30 foot drain camera delivered today, along with some vacuum and pressure gauges. My plan is to give my boat a colonoscopy tonight. I'll send it up the intake (from the strainer) so I can have a look at the input side of the fuel cooler.

I am thinking about removing the hose from the seacock, putting the camera in the closed seacock, seal it up the best I can with some towels or something. Then open the seacock and shove the camera down to look at the intake scoop from the inside. Hopefully the bilge pumps can keep up... :wow:

If I don't find anything, I am going to hook up the gauges to the various zinc locations in the sea water circuit and compare with the port side. Hopefully I can at least isolate where the obstruction is.

 

[douglee25]

I don't know your engine specifically but an engine that doesn't overheat at idle but at speed is usually a flow issue (which you diagnosed correctly). Is it possible though that it's something with the pump and or impeller? Maybe you trashed the impeller when you sucked up the debris.

Doug

Edit - I would also pull that initial hose right off the seacock and look through both sides. I think Gary or someone else I can't remember experienced something similar with an engine or AC system?

Also read Gary's post here. He talks about a cam button.

http://clubsearay.com/showthread.php/9428-QSM-11-spare-parts-list?highlight=seacock+clog+hose

 

[mistercomputerman]

I think the story was that GW had oysters growing in his one of his pickups and the shell was acting like a flap.

 

[douglee25]

That's right. Good memory. Something easy to check anyway.

Doug

 

[Greg]

Fixed. I pulled the hose off the strainer leading to the fuel cooler, sent the camera down and found a wad of fishing line and plastic like seaweed trapped between the zinc and the inlet. with the help of some tweezers, a dental pick, and a crab pick, I was able to extract it all.

The only way I can think that it got by the strainer is that when I pulled the strainer out, it was full to the top. Maybe it was still in the inlet hose and leaked passed while I was cleaning the strainer. It probably got hung up on the zinc during the backflush.

So much for my awesome fuel economy the past couple of weeks.

 

[mistercomputerman]

Glad you found it. We want the boat to be in tip-top running order when we come to pick it up for our fishing trip on July 7th while you are out of town camping in the woods.

 

[douglee25]

Nice find!

Glad you figured it out.

Doug

 

[cod]

Good job Greg..... To be clear, was the debris trapped between the zinc on the fuel cooler and fuel cooler inlet where the hose is connected?

 

[Greg]

Glad you found it. We want the boat to be in tip-top running order when we come to pick it up for our fishing trip on July 7th while you are out of town camping in the woods.

You guys are still going forward with that silly trip? I thought we were all going camping? I hear Dolly Parton may be there.

Good job Greg..... To be clear, was the debris trapped between the zinc on the fuel cooler and fuel cooler inlet where the hose is connected?

No, it was stuck right on the inlet side of the tubes. It passed the zinc on the way in. I was trying to figure out how come the backflush didn't get it out. The only thing I could think is maybe it got stuck on the zinc during the backflush. Although it went right by it on the way in.

 

[Alex F]

Nice job, Greg. I'm glad you finally found it. I would still think that BB/GSB sea strainers would prevent this from happening. I didn't have them on my 320DA and my scoop strainers and sea strainers were getting clogged all the time. My 420 has them installed and I just never have to clean a single seaweed from the strainers. It's a truly a night and day difference.