Issue with engine power after replacing mixing elbow

Brinky63

Brinky63

.
Oct 14, 2017
89
HUnter 306 Aruba
I had an issue with my mixing elbow on my yanmar 2GM20F recently which i was able to remedy with the help of many on SBO. Thanks for the help all.

Since replacing the mixing elbow I've serviced the engine replacing all filters, oil and water just to get a clean slate.
When I place her in gear and move the throttle for power i noticed that i now need to move the throttle lever further to get the rpm's (i.e. power) i want.
When troubleshooting the issue with the mixing elbow i remember that:
  • air was actually coming out of the air intake thus we had some smoke in the cabin.
  • when mixing elbow was removed the thing was so clogged no water passed thru.
I gather that this back draft of smoke will have passed thru the engine and effected the internals. What suggestions do you all have for a next step to service the engine?

On a lighter note, does anyone have a replacement part code for the Yanmar 128270-12540 air filter from Napa?
 
kloudie1

kloudie1

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Nov 6, 2006
9,892
Hunter 34 Mandeville Louisiana
Air Filter: I took some 1/4" thick air filter foam that I got from a hardware store and re-wrapped the old Yanmar perforated metal stiffener .. the Yanmar foam becomes brittle and gets eaten by the engine .. the new foam does not disappear like the old original foam did.
 
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RoyS

RoyS

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Jun 3, 2012
1,742
Hunter 33 Steamboat Wharf, Hull, MA
First I would set valve lash. While doing that inspect valve operation for sticking valves, broken springs and the like. If that fails to stop your blow-by issue, then remove the head for a total valve job. The rings would be next but let's hope that is not necessary. Good luck.
 
seadaddler

seadaddler

.
Dec 19, 2006
5,809
Hunter 36 Punta Gorda
Are you sure you did not do something to the the throttle cable adjustment,but how does the engine run and does the motor power up and move the boat up to hull speed.
You could get each cylinder checked for compression before doing any work on the head.
Nick
 
Brinky63

Brinky63

.
Oct 14, 2017
89
HUnter 306 Aruba
RoyS thanks for the info. I don't have blow back issues anymore. Exhaust and water coming out perfectly and intake is good and strong. My thought is that the injectors are filthy and need cleaning.
 
Brinky63

Brinky63

.
Oct 14, 2017
89
HUnter 306 Aruba
Seadaddler, thanks for the reply. we checked the cable and all looks good. Engine runs great in neutral and in gear, powers up like a charm. Boat gets to hull speed with no issue just need to push the lever over more then usual.
My train of thought is what happened to the engine when the mixing elbow was clogged. The air was coming back out thru the engine out via the air intake into the cabin. What damage could that have caused to the injectors and cylinders.
Also where did the water go since it could not get out. does it have a chance to blow into the engine via the plugged mixing elbow?
 
Brinky63

Brinky63

.
Oct 14, 2017
89
HUnter 306 Aruba
kloudie1, is that equivalent to the air filter foam they use for split unit ac's?
 
LeslieTroyer

LeslieTroyer

.
May 20, 2016
3,014
Catalina 36 MK1 94 Everett, WA
Measure the intake diameter and get a k&n filter. That fits. Works great on my Universal M25. I also drilled a hole in the filter base and installed a barbed fitting for the breather tube.
 
AlexB

AlexB

.
Aug 9, 2016
37
C&C 36 Great Kills harbor.
Brinky63 said:
I had an issue with my mixing elbow on my yanmar 2GM20F recently which i was able to remedy with the help of many on SBO. Thanks for the help all.

Since replacing the mixing elbow I've serviced the engine replacing all filters, oil and water just to get a clean slate.
When I place her in gear and move the throttle for power i noticed that i now need to move the throttle lever further to get the rpm's (i.e. power) i want.
When troubleshooting the issue with the mixing elbow i remember that:
  • air was actually coming out of the air intake thus we had some smoke in the cabin.
  • when mixing elbow was removed the thing was so clogged no water passed thru.
I gather that this back draft of smoke will have passed thru the engine and effected the internals. What suggestions do you all have for a next step to service the engine?

On a lighter note, does anyone have a replacement part code for the Yanmar 128270-12540 air filter from Napa?
Click to expand
it looks like cloged exhaust.
 
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AlexB

AlexB

.
Aug 9, 2016
37
C&C 36 Great Kills harbor.
Brinky63 said:
Seadaddler, thanks for the reply. we checked the cable and all looks good. Engine runs great in neutral and in gear, powers up like a charm. Boat gets to hull speed with no issue just need to push the lever over more then usual.
My train of thought is what happened to the engine when the mixing elbow was clogged. The air was coming back out thru the engine out via the air intake into the cabin. What damage could that have caused to the injectors and cylinders.
Also where did the water go since it could not get out. does it have a chance to blow into the engine via the plugged mixing elbow?
Click to expand
no damage, just check if muffler also cloged. Diesel Engine does not like backpressure. on my boat there is no dust-no need for air filter at all.
 
Last edited:
Tipsynippertoo

Tipsynippertoo

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Jul 1, 2017
64
Hunter 356 Brightlingsea
If the engine will make the rpms and give you hull speed then I suspect you are chasing a ghost...injectors spray at such high pressure that a slight increase in combustion chamber pressure will make very little difference.
How many hours does the engine have total time? How many hours operated with the exhaust blockage?
If the engine is up at around 2000 hours it would be a good time to do a de-coke and replace the valve stem seals anyway, and have the injectors overhauled.
BUT, if it starts from cold easily (always a good test of a diesel engine) and is producing the power it always did you are worrying unnecessarily. You have probably disturbed the throttle linkage whilst working on the engine, or, you are more sensitive to the engine and are imagining it.
Regarding the foam for the air filter.....not all foam is the same. Something robbed from upholstery my restrict the airflow. If you are not in a dusty area then leave the steel mesh in there, and order a new genuine air filter and replace it later. Although the air filter may look simple, they are usually designed to work in sympathy with the engine, and perform a degree of "tuning" of the whole manifold assembly......at least they do in modern cars!
Good luck.
Neil
 
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Apex

Apex

.
Jun 19, 2013
1,197
C&C 30 Elk Rapids
Tipsynippertoo said:
If the engine will make the rpms and give you hull speed then I suspect you are chasing a ghost...
.......You have probably disturbed the throttle linkage whilst working on the engine, ....
Neil
Click to expand
If the engine is running well, and just the throttle cable needs to move, I suspect there is nothing but cable adjustment needed. Do you have separate gear and throttle cables?
 
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Brinky63

Brinky63

.
Oct 14, 2017
89
HUnter 306 Aruba
AlexB, both water and exhaust come out clean and good at the stern. Will check just to be safe. Will also check the throttle linkage to see if that might be the case.
 
Brinky63

Brinky63

.
Oct 14, 2017
89
HUnter 306 Aruba
Tipsynippertoo. Not sure how many hours the engine has. Don't think the complete blockage had more then 2 hours of operation. We've owned the boat for 8 years now and have no more then 100 hours no the engine, the previous owner could not have amassed that many hours either since the boat is now 16 years old.
Engine starts up cold without issue.............
Will get a proper air filter.
Thanks for the input.
 
Brinky63

Brinky63

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Oct 14, 2017
89
HUnter 306 Aruba
Apex. Single throttle cable for rpm's and forward/revers. Will take a look at it.
thanks for the input.
 
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AlexB

AlexB

.
Aug 9, 2016
37
C&C 36 Great Kills harbor.
Sure, you said, that elbow was clogged. What was there? Maybe same stuff stock on muffler. As I said before, diesel hates back pressure, even if it's not blocked completely, but reduces flow, it affects performance .
 
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Brinky63

Brinky63

.
Oct 14, 2017
89
HUnter 306 Aruba
Alex,
This is what the mixing elbow looked like when i removed it. Not sure how much crud went into the muffler. Will research how i can check and clean that. In the state it was in below not even water passed thru meaning no air either. I had air coming out of the air intake on the port side of the engine and had no power.

I'm just wondering if the exhaust going back into the engine can harm the internals.

Also what happened to the water that could not make it out? Does the mixing elbow have a control valve or something similar that prevents water from backing into the engine. It is seawater so we don't want that.

 
Brinky63

Brinky63

.
Oct 14, 2017
89
HUnter 306 Aruba
smoke comes out just fine as does cooling water. will have to get back to you on the muffler.
 
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