Blocked Heat Exchange Discharge Fitting

Hugh17 · January 03, 2018, 08:29:49 AM

I have the Universal M25 with the 2" Heat Exchanger. I've had the Heat Exchanger off for professional cleaning as well as increasing the size of the discharge fitting for the raw water. I've had repeated issues with blockages inside this fitting. It's easily resolved by breaking the blockage with a screwdriver and then blowing through the HX through the hose from the raw water pump. My question is WHY IS BLOCKAGE OCCURRING AT THIS FITTING?

Stu Jackson · January 03, 2018, 08:44:13 AM

Do you sail in salt water? If so, it is the salt precipitating out. I had this issue with our 2" HX when we bought our boat in 1998. I eventually upgraded to a 3" HX.

Hugh17 · January 03, 2018, 08:48:36 AM

Yes, salt water. Wonder why it's a problem with the 2" HX and not the 3" HX?

Ed Shankle · January 03, 2018, 09:25:14 AM

I've had that problem a couple of times with my 3" HX, so it isn't limited to the 2". I haven't tasted or tested it however. I figured it was calcification, not salt. Sort of like how an oyster shell grows.

Regards,
Ed

Stu Jackson · January 03, 2018, 02:30:17 PM

Quote from: Hugh17 on January 03, 2018, 08:29:49 AM
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through the HX through the hose from the raw water pump. My question is WHY IS BLOCKAGE OCCURRING AT THIS FITTING?

Hugh, some further thoughts on this ^^^^ in particular.

The inlet from the raw water pump is cold(er) seawater. That point is where it FIRST hits the really hot engine coolant at the HX. The raw water is in the shell, with the coolant in the tubes. As the raw water hits the hot shell at that inlet is where the first salt "dropouts" tend to "hang out."

As Ed says, it is not limited to the 2" HXs and I've mentioned it a number of times here on the forum, as well as in some of my Secretary reports in Mainsheet magazine. I recommend removing the HX periodically - everyone has a different zinc disintegration rate. In California from 1998 to 2016 I was changing zincs every three or four months. So I removed the HX maybe every two or three years, usually when I was doing other engine work, like the muffler and riser replacement (in Tech Notes, probably sometime in 2016). Here in British Columbia's Gulf Islands I have found zinc replacement necessary only every six months, or double the time between changes from California!!! So, I figure sometime in 2019 I'll have to do it again.

It's not a bad idea to do so, since you'll want to remove and replace coolant at the same time. Rather than having the coolant run out until it reaches level with the bottom hose outlet (some remains in the manifold) I drain it into a bucket from the Toyota 90 degree elbow under the coolant pump, with a photo as shown on the "How to Burp Your Engine" in the 101 topics thread. Sometimes I keep the coolant and pour it back in, other times I use it as an opportunity to replace the coolant, or most of it at least. I also have never had any issues with tubes, since the water flows so quickly through them, of course using the engine a lot helps.

I think I am on my second 3" HX, 'cuz the first one's shell got punctured by a broken support bracket that I discussed with photos in the "Good Guys from Sendure" topic (http://c34.org/bbs/index.php/topic,6920.0.html), also in the 101 Series. I got the second HX from Seakamp in 2012 ($488), the first one was from Universal purchased in 2001 and installed in 2003 ($300).

Hugh17 · January 03, 2018, 03:05:23 PM

Stu,
The blockage issue I have is in the HX raw water discharge fitting not the water coming in. See the picture below. The green arrow indicates the fitting where the blockage occurs. Additionally, the blockage is always deep in the fitting, where the HX water chamber and fitting meet.

Stu Jackson · January 03, 2018, 05:32:54 PM

Hugh, it could be that I got it bass-ackwards and the salt drops out after the water cools down. It's been awhile since I practied my engineering heat transfer. As to why it's deep inside, I do not know.

End result is almost identical: a pile of crud inside, at or near the port.

Solutions is also identical: remove HX and check ports.

Nice engine, it's only the second one I've seen out like that. Great job on the oil breather hose, too.

Hugh17 · January 03, 2018, 07:02:57 PM

Stu,
I suspect as you do that the the salt deposit crude is caused by the change of temperature as the water exits the HX. I can unblock the fitting, but I'm trying to figure out a way to prevent it. One possible solution I'm considering is to rig up a fresh water flushing system so I can clean out the HX before shutdown.

The engine picture in the preceding post was taken prior to installation a couple years ago. I've recently upgraded the air filter with a K&N RU-2450 and a custom made intake manifold fitting to accept the breather vent hose.

Jon W · January 03, 2018, 09:04:00 PM

What kind of fitting do you have on the discharge? Straight or 90 degree elbow?

britinusa · January 04, 2018, 02:22:42 AM

Just a Quick Thank you for posting those pics

I read every new post on the site and it's amazing how much I learn just by looking at the pictures that folks post (as well as the text

)

That first picture, of the engine on blocks, does a great job of showing how the engine could be mounted during out of the boat service, if when ever I need to go that far.

Paul

Ed Shankle · January 04, 2018, 09:50:59 AM

Each time I've had the problem it's been on the raw water inlet, about a 1/2" deep, just before the 90* elbow. I can break it up with a screwdriver. Interestingly, it's wafer thin and builds up from the edges inward. I have noticed once before however, when I had the end caps off prior to having it acid washed, a very small mollusk shell in the HX! A blockage in the making! Makes me think that it's possible a seed small enough to get thru the strainer can potentially latch on somewhere in the HX and grow.
Regards,
Ed

KWKloeber · January 04, 2018, 01:50:57 PM

Jim

Which deg F thermostat is installed? I presume you are in salt.

k

Stu Jackson · January 04, 2018, 01:52:00 PM

Quote from: Hugh17 on January 03, 2018, 07:02:57 PM
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I can unblock the fitting, but I'm trying to figure out a way to prevent it. One possible solution I'm considering is to rig up a fresh water flushing system so I can clean out the HX before shutdown. >>>>>>>>>>>>>>>>>>>
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Hugh,

I've learned that often additional "add-ons" have unintended consequences with sometimes bad results.

Given the "work" involved in removing and replacing the HX once very three to five years, based on what I see from my operating temperature and the zincs, I wouldn't recommend it.

My effort went into installing the larger HX.

Your boat, your choice.

PS - I have a 180F thermostat with both a 160F and a 180F as backups.

Hugh17 · February 12, 2018, 06:13:06 AM

Quote from: Jon W on January 03, 2018, 09:04:00 PM
What kind of fitting do you have on the discharge? Straight or 90 degree elbow?

It's a straight fitting. Scroll up a a few comments and you'll see a good picture of the HX with the fitting.

Hugh17 · February 12, 2018, 06:16:55 AM

Quote from: KWKloeber on January 04, 2018, 01:50:57 PM
Jim

Which deg F thermostat is installed? I presume you are in salt.

k

Yes, I'm in salt water. I've not removed the thermostat so I'm not sure about this, but since the coolant temperature shows as 160 degrees on the gauge I assume it's 160. The temp will run up higher if I run the engine above 2800 rpm.