Yet another Yanmar overheating issue

geoffschultz

geoffschultz

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Feb 3, 2009
270
Freedom 40/40 Rio Dulce, Guatemala
I have a 1997 Yanmar 3JH-2TE (turbo) with 5500 hours on it which is overheating when I push the RPMs above 2500. At 2500 I'm at 185, and it goes up from there. This has been going on for multiple years, but is getting worse, meaning the the highest RPM that I can run at is dropping. Several years ago I could run at 2800.

Last year I did an extensive overhaul of the engine which included the following:
  • Removed and acid-boiled the heat exchanger
  • Replaced the thermostat
  • Removed and inspected the mixing elbow - like new
  • Replaced water hoses to mixing elbow
  • Replaced the raw water pump and impeller. The water flow is good out of the exhaust.
  • Replaced the water hose to the heat exchanger
  • Flushed cooling system with fresh water until it ran clear. This was done on the hard, so the engine wasn't run.
  • Replaced coolant - red. Completely full upon inspection. Expansion tank full.
  • Replaced some hoses
  • Mechanical stuff like replacing motor mounts, clutch work, transmission work, etc
I'm in Belize where the water temp in is in low 80s. I'm completely stumped as to where I should be looking next.

Thanks for any suggestions that you can provide! -- Geoff
 
Mark Maulden

Mark Maulden

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Jan 25, 2011
2,402
S2 11.0A Anacortes, WA
Im assuming you replaced the raw water hose and valve fro the thru-hull to the strainer? Check the strainer for obstructions? Hose from strainer to raw water pump? And on up the line through the exchanger and also exhaust hose? Is the thru-hull clear? Fresh water pump? Don’t just look at the outside of hoses and assume they’re good.
 
Scott T-Bird

Scott T-Bird

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Oct 26, 2008
6,083
Catalina 320 Barnegat, NJ
This may be a dumb question, but if everything is functioning properly, are you sure that you are actually over heating? What if your sensor is faulty or not in the right location to react accurately? You make it sound like the raw water side is functioning fine. The only thing it seems you haven't verified is decent flow of coolant from the freshwater pump as @Mark Maulden questions.
 
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geoffschultz

geoffschultz

.
Feb 3, 2009
270
Freedom 40/40 Rio Dulce, Guatemala
Mark Maulden said:
Im assuming you replaced the raw water hose and valve fro the thru-hull to the strainer? Check the strainer for obstructions? Hose from strainer to raw water pump? And on up the line through the exchanger and also exhaust hose? Is the thru-hull clear? Fresh water pump? Don’t just look at the outside of hoses and assume they’re good.
Click to expand
I forgot to mention that I also put on a new 1” thru hull that feeds a Groco strainer with 3/4” fitting. All new hoses between the thru-hull and the strainer.

The strainer is fine. Good water flow out exhaust.
 
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geoffschultz

geoffschultz

.
Feb 3, 2009
270
Freedom 40/40 Rio Dulce, Guatemala
Scott T-Bird said:
This may be a dumb question, but if everything is functioning properly, are you sure that you are actually over heating? What if your sensor is faulty or not in the right location to react accurately? You make it sound like the raw water side is functioning fine. The only thing it seems you haven't verified is decent flow of coolant from the freshwater pump as @Mark Maulden questions.
Click to expand
I have instrumented it with a thermocouple on the sender unit. It reads 10F below what the instruments reads, but tracks the temp. So I believe that it is running hot.
 
Scott T-Bird

Scott T-Bird

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Oct 26, 2008
6,083
Catalina 320 Barnegat, NJ
Hmmmm ...my instrument reads about 10F below the actual temp. Perhaps the issue is with the freshwater pump? It still sounds to me like the raw water side is good and the exchanger sounds like it is open. You've replaced the thermostat and I can't say that I ever hear that thermostats are particularly troublesome.
 
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ggrizzard

ggrizzard

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May 27, 2004
1,976
Hunter 30_74-83 Ponce Inlet FL
If you hire a mechanic to trouble shoot your engine he will ask these questions
after you tell him what you've already done:

Is the exhaust showing any steam or white smoke?
Is there any coolant leak?
Is there any "milky" stuff in the oil sump?
Have you done a compression test on all cylinders?
Last question...
Have you sacrificed a virgin to Poseidon? :laugh:
Sorry, I couldn't resist. I know this situation is driving you crazy.
Keep us posted.
G.
 
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garymalmgren

garymalmgren

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May 29, 2018
461
Canel 25 foot Shiogama, japan
Run the engine until it is warm.
Disconnect the raw water line where it injects into the exhaust elbow.
Run that line into a big bucket and run engine.
If the raw water exits hot to warm you are getting heat transfer from raw water to coolant ( which is what you should have).
If the raw water doesn't get hot or quite warm (you are starting with 80 degree sea water) you have a problem with heat transfer from coolant to raw water.
That will narrow down the side of the cooling system that you have a problem with.
As you have gone through everything on the raw water side it looks like something is weird on the coolant side.
An airlock or something out of the usual.

Yanmar 3GM30F cooling system problem - Page 2 - Cruisers & Sailing Forums

Originally Posted by gamayun Ah, now I know why I don't live in areas where it freezes! Andrew, did you check the pump impellor to make sure nothing got damaged during those 5 minutes you had it on?
www.cruisersforum.com

Yanmar 3GM30F cooling problem - urgent advice needed please

Hi there, Whilst in the marina I thought I'd change the coolant in the motor as I'd been meaning to do it for a very long time. I did it, brought the engine up to operating temperature and all seemed fine. Today I finally got the weather to make the passage across Biscay to Falmouth and 10...
forums.ybw.com forums.ybw.com

Hope this helps a little.

gary
 
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kloudie1

kloudie1

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Nov 6, 2006
9,894
Hunter 34 Mandeville Louisiana
I had a problem with the seawater strainer gasket leaking air into the pump intake line at higher rpm. Water always flowed well, but the decrease in flow was not noticed. Once the strainer was rebuilt the overheat at high rpm stopped. The old cork gaskets in the Groco strainer had compressed and had minute cracks. No visible leaks of water were noticeable but there were green corrosion traces around the top gaskets.
 
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M

MitchM

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Jan 20, 2005
1,021
Nauticat 321 pilothouse 32 Erie PA
when was the last time your turbo was serviced ? boat diesel.com (50$/year ) has a number of threads on what happens when yan turbos are not serviced per yan mar specs. i read it too long ago to remember all the bad stuff that can happen. . ..
 
Captain Larry-DH

Captain Larry-DH

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Jun 14, 2010
2,096
Robertson & Caine 2017 Leopard 40 CT
Does it have a sail drive? If so does it use one of those gate valves that take 22 half-turns to open? Those those gate valves are known to have poor flow problems. Also, if there is a flow restriction within the sail drive (e.g. sucked in a plastic bag or sea creature)? You can try back-flushing a sail drive by adapting a garden hose to the intake hose.
 
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