How long mixing elbows last/reduced flow

Oct 9, 2008
1,739
Bristol 29.9 Dana Point
-update 11/13 below-
How long do mixing elbows last?
Mine in 6 years old. About 300 hours. Looks new (pic).
....on the outside.
I suddenly have reduced raw water flow. Pacific salt water last 2 years. Upper Chesapeake previous 4.
I checked the through hull inlet, gusher. Checked sea strainer outlet, much less water. Yet no restrictions. I put the strainer in 2 years ago. Boat didn't have one previous 32 years.
So I bypassed the strainer. Same low flow at the exhaust. Maybe a quarter of what it should be.
Very recent impeller. Oberdorfer pump. But put another new impeller in just to check. Same problem.
I had checked the HX a couple months ago, looked clear. But it's the original (1984) Universal 2" with only 1 end cap. Can't see the zinc pencil end, but poked around in there with a wire and it seemed clear.
I'm wondering is it the HX clogged where I can't see it, or the mixing elbow. Or...
Any comments appreciated.
 

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Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
They last as long as exhaust manifolds. They do require the occasional cleaning though if you operate the engine at low power levels a lot.
Your gusher at the inlet thru-hull and no gusher at the strainer is probably because the strainer is higher up nearer the water line. a strainer above the water line will not even have water flow!!!
think you diagnosed the problem by tracing along the flow path. has to be the HX or elbow.
 
Feb 26, 2004
22,760
Catalina 34 224 Maple Bay, BC, Canada
I checked the through hull inlet, gusher. Checked sea strainer outlet, much less water. Yet no restrictions.
How can there be less water there if you say "no restrictions"?

Unless Bill is right in his assumption. My strainer is below the waterline.
 
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Jan 27, 2008
3,045
ODay 35 Beaufort, NC
What kind of mixing elbow do you have? Is there a 90 degree fitting? Those can clog with salt. Do you have flow at the hose going into the HX? Do you have flow at the hose going into the mixing elbow?
 
Mar 29, 2017
576
Hunter 30t 9805 littlecreek
yes check that 90 deg fitting right where raw water goes into exhaust elbow the cold salt water hits hot exhaust steel and evaporates and causes a salt blockage if ya can trade out that fitting for a straight
 

NYSail

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Jan 6, 2006
3,049
Beneteau 423 Mt. Sinai, NY
Pull the water inlet hose off the elbow and see flow...... then if nothing odd just remove the elbow itself
And inspect. My yanmar elbow was good for 9 seasons before it clogged. Some people just clean them...... I am of the replace school if they are bad.
 
Oct 9, 2008
1,739
Bristol 29.9 Dana Point
Thanks all.
Great idea to check the flow at the HX outlet/elbow inlet. I sort of thought of that but didn't want to climb in the rear -engine access, have salt water in the engine bay to rinse and clean, etc. Lazy! After I'd been wrenching an hour, just wanted answers. The answer is continue checking the flow further downstream.

So I've never cleaned an elbow.
If this turns out to be the problem...
Do you just remove it and reach in the ports with tools? Can you get all the up to the angle? Any hints.
 

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Oct 22, 2014
352
Pearson P303 #221 RockPort Maine
My engine is a 2GMF and installed a new elbow 4 years ago. Upon inspection each year I've noticed a buildup each year more year 2 and a lot year 3. It seems to build up faster when the old buildup isn't removed and put back into service. It does seem though the exhaust oil/fuel collects more when its cool. So I myself will remove and clean every 3-4 years baring any issues. I put mine into the oven and did a clean-cycle. when done it looked new.. But that's me! However, Make sure you soak in hot water for a day before putting into oven. It prevents a possible fire. lol
Regards Capt. Rob
 
Jun 8, 2004
2,841
Catalina 320 Dana Point
On my Perkins the elbow was just a 45 degree bend and would last 600 hrs. before the exhaust passage would clog. I cleaned it once using a grinder with a round rotary rasp on it, took 2 days and made an incredible mess. The "coke" that forms is hard as a rock. A couple days later while at a radiator shop leaning on a bead blasting cabinet a better possible method dawned on me :banghead:. The 3 piece 180 degree elbow on the Yanmar I replaced right after I got the boat at 300 some hrs. and recently again at 650 when it clogged, partly my fault, I don't run it much or hard enough. Part of the problem with cleaning them is the water passage runs up around the bend and it's mostly inaccessible.
 
Jan 22, 2008
1,654
Hunter 34 Alameda CA
yes check that 90 deg fitting right where raw water goes into exhaust elbow the cold salt water hits hot exhaust steel and evaporates and causes a salt blockage if ya can trade out that fitting for a straight
I have to clean mine every season just so it won't clog up. See photo.
20160211_154450.jpg
 

Rick D

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Jun 14, 2008
7,132
Hunter Legend 40.5 Shoreline Marina Long Beach CA
When I had a 3GM, I had elbow problems at the injector. I purchased a stainless steel spring, about 6" long and put it in the bit of my drill and, while squirting carb cleaner, ran it in and out few times. Kept it clean. Did it once a year.
 
Jan 22, 2008
1,654
Hunter 34 Alameda CA
When I had a 3GM, I had elbow problems at the injector. I purchased a stainless steel spring, about 6" long and put it in the bit of my drill and, while squirting carb cleaner, ran it in and out few times. Kept it clean. Did it once a year.
I'm intrigued by this. Is it a long, small diameter spring? So you can Roto-Rooter the entire water passage part of the elbow through the little (3/8" NPT) hole?
 
Mar 29, 2017
576
Hunter 30t 9805 littlecreek
I blame the 90 deg. Slows the water down or something straight fitting seems to fix
 

Rick D

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Jun 14, 2008
7,132
Hunter Legend 40.5 Shoreline Marina Long Beach CA
I'm intrigued by this. Is it a long, small diameter spring? So you can Roto-Rooter the entire water passage part of the elbow through the little (3/8" NPT) hole?
It worked for me. The passage that was carbonized was at the elbow's junction with the pipe nipple. And the spring moving around seemed to clear (with the carb cleaner) the immediate area. Yes, small OD spring in a drill chuck. Actually, it may not have been SS; probably wasn't.
 
Oct 9, 2008
1,739
Bristol 29.9 Dana Point
YIKES!
Good idea to check the raw water flow at the elbow inlet.
Disconnected the hose, put bucket under it, turned motor on.
Trickle. Like a dog peeing. Maybe a quart a minute.
So it's the HX.
I decide to check the pump output just in case. Remove the HX raw inlet hose at the bottom of the HX, and see this:
image.jpeg


The odd thing is that the rods are clear inside.
 
Oct 9, 2008
1,739
Bristol 29.9 Dana Point
Turned out only that HX inlet elbow was clogged. Minor calcification elsewhere. Cleared it out. Also replaced the hose from pump to HX; it was too small a diameter and a hodgepodge of 2 lengths of hose (pic). Probably from when the yard monkeys installed the new Oberdorfer pump 6 years ago. - I should have done it myself.

I think the raw water filter I installed 2 years ago restricted the flow, causing calcification to build up.
It never caught anything other than little plant bits, and the motor ran without it for 32 years previous. So I removed it.

Rapid flow now. Didn't have to replace HX nor mixing elbow.
Total repair cost: $8. (Hose)

image.jpeg
 
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Dec 1, 1999
2,391
Hunter 28.5 Chesapeake Bay
The OEM mixing elbow on my 1986 Yanmar 2GM20f lasted about 25 years...and it was nice enough to give plenty of early warning (reduced max rpms) that it required attention.
 
Jan 22, 2008
1,654
Hunter 34 Alameda CA
The OEM mixing elbow on my 1986 Yanmar 2GM20f lasted about 25 years...and it was nice enough to give plenty of early warning (reduced max rpms) that it required attention.
Yes, mine lasted 25 years as well. But it wasn't as kind to me when it broke in half. Other than the annual cleaning of the water inlet fitting, I only cleaned the rest of it a couple of times during that period. I am going to change that little fitting to a straight one and am looking forward to trying the spring that Rick D has posted about for annual cleaning. The close nipple with both left and right hand threading is a real weak point. It's made of stainless and can only be inspected easily by complete disassembly. I have located a reference to a black iron or galvanized right hand/left hand 1-1/2" NPT threaded hexagonal nipple here:

http://www.gfps.com/appgate/ecat/common_flow/100071/FIT/en/497226/497233/P121799/product.html

I haven't followed up on it as a potential spare that might last longer as its the same material as the two cast pieces of the exhaust elbow.
Broken.JPG
 

MitchM

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Jan 20, 2005
1,011
Nauticat 321 pilothouse 32 Erie PA
i remember quite a struggle replacing a yan 2 gm exhaust el in 2002 because the one end was regular thread right - makes - tight , but the other end was reverse thread right -makes - loose. are they still doing that ?