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Old 27-09-2010, 18:51   #1
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How Do I Know if My Turbo Is Operating Properly ?

Hi all,

Yanmar 4JH3TE Engine with ~450 hours. I used to notice a distinct turbo whistle from the engine at mid to full revs.

The other day whilst pushing against some chop, the engine did't really seem to be giving it's previous best which got me listening for strange noises.

Oddly it seems to my ears, that I'm not getting quite the same note from the turbo as before.

Question : How would I know if the turbo was failing to kick in ? Would I definately see a change in the exhaust color ?

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Old 27-09-2010, 19:04   #2
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Do you have any turbo instrumentation on your engine pannel like vacuum or pressure "Boost" gages?
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Old 27-09-2010, 19:09   #3
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Old 27-09-2010, 19:53   #4
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If memory serves that is a KKK (Borg Warner) turbo... there should be a test port on the pressure side of the compressor to measure boost... Again from memory (Don't flame me if I'm wrong) I think it is about 14psig of boost UNDER FULL LOAD/THROTTLE. An unloaded full throttle engine will be a LOT less.

Less accurate checks would be to remove the clamp on the intake side and see if the turbine is clean and rotates freely. If it has any resistance, check the exhaust side, it may have some rust on the housing from an old mixing elbow misting water back after shut down. If the resistance does not allow the shaft to spin freely, the bearings may be going.

Overhauling the turbo is not a big deal IF you don't damage a fin or bend the shaft in any way (Yanmar's shop manual has a pretty good explanation). If the turbo shaft or fin(s) are even nicked, they will need to be re-balanced, and that is outside the realm of a DIY job.

ETA: If you need a cheap way out... I think Mitsubishi used that turbo in one of their cars and eBay has a few listed... be careful to match it up carefully, as some were water cooled and some were not

More ETA: If the turbo was not "kicking in" as you said, the engine will not come up to speed, and likely will have black smoke
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Old 28-09-2010, 10:28   #5
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Thanks for the replies.

I just had a good look at the tuirbo. It says it comes from "IHI Corporation".

The shaft seems to turn without grittyness or sticking. I can run up the engine and with the flame arestor removed I can see the turbine spinning. But I'm struggling to hear the normal whine when it's up to speed.

I can see a plug on the exhaust side of the turbo, but none on the inlet. I assume it is inlet pressure I should be measuring.

I have been monitoring the exhaust colour for a while and whilst there is no excessive smoke, there is a little more grey smoke than I expect.

The service manual says to take a listening stick and put it against the shaft housing, then listen for noise every 2 -3 seconds. I guess I'll try this next.

Eventually I should get a set of gaskets and pull the thing apart to do some micrometer checks on the shaft etc. The tolerances are all in the service manual.

On a separate thread (no replies yet) I asked about what liquid to use to wash the turbo, I beleive that Mack Boring has a special (expensive) fluid, but there is also a home made concoction. Anyone know what this is ?

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Old 28-09-2010, 12:01   #6
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If your boat was originally propped correctly and you can still run up to rated rpms at wot (3,600 I think), then your turbo is definitely working ok. Heavy black smoke at about 2,000 rpm would be a symptom of a stuck turbine.

With regard to the wash issue, do a search on boatdiesel. This has been thoroughly discussed. In summary add about a half ounce of Dawn or similar to a quart of water in a spray bottle. With your air filter removed and at cruising rpm, slowly squirt (over a 1-2 minute period) a quart of the soapy water in the turbine inlet. Repeat with fresh.

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Old 28-09-2010, 12:28   #7
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Thanks David,

That's the one. I have the service manual, but this process isn't in it.

I'll see if that makes any difference as I can't see that there's any downside in doing the procedure.

Engine revs to around 3700 at WOT, but I notice that if I open the throttle to 3100 and leave it there, the revs die back over 5 - 10 seconds to around 2,700. Wasn't sure if this was a sign of a filter starting to clog or if there's some friction plate on the throttle linkage which is loosening up. Will investigate and report.

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Old 28-09-2010, 12:46   #8
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When I had one my mechanic sold me 2 oz of a cleaning agent. Apparently it builds soot in the blades. Cleanig was very easy you just have to be carefull with the cleaner. I just found this article online which is what I did w/mine.



If the engine begins to smoke while underway firstly check the hull and propeller for fouling, the injectors for condition and the turbocharger for damage. If these are all OK, TURBOWASH the turbocharger.
TURBOWASH is a genuine Yanmar part, dont let any ignorant dealer tell you otherwise. The dealer should be repacking the TURBOWASH from the large container and selling it in 250cc / 8oz bottles, not fitting you up with a lifetime supply!
  • Thunder down the harbour with the engine at 75% load and spray up to 25mls of TURBOWASH into the air intake over about 15 seconds.
  • Wait a bit
  • Spray an equivalent amount of clean fresh water into the air intake
  • If it doesnt come clean, try up to 4 times.
In some manuals Yanmar recommend using dishwashing liquid if TURBOWASH is not available. In my experience it doesnt do the job whereas TURBOWASH cleans right around the bend. I can only recommend the proper product, it really works!
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Old 28-09-2010, 18:09   #9
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When was the last time you changed your fuel filters? I drive a Dodge Cummins is a pure dog if I don't change filters around every oil doesn't hesitate at first, just loses power..

With a stuck or slow turbine it will bog pretty bad..make sure the turbine bearings are getting fresh oil..boost should not be greater than about 14.7 lbs per in square in a normal application..
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Old 28-09-2010, 19:01   #10
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Originally Posted by zopi View Post
When was the last time you changed your fuel filters?
Check all of your filters. I've seen air filters so clogged that the engine would run but couldn't move the vehicle (not a boat). Check for possible exhaust restrictions too. I'm not saying this is the problem, but it's an easy check of something that could cause a modest loss of performance, especially in a turbocharged engine.
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Old 11-10-2010, 05:10   #11
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Update: perhaps going down the wrong road here

Hi all,

So I've now taken some more advice from a couple of Yanmar dealers and changed the filters and had a further think and this is where I am now :

The concerns that I had were :-

a) I couldn't hear the turbo operating any more.
b) I wasn't getting the speed I expected even with a pretty clean hull
c) I seemed to be getting a little more smoke than I expect

I cleaned the filters with no change in performance or smoke.

I checked the speeds at various engine RPM's and double checked that the tacho was accurate with a separate photo tach. Here are the results :-

RPM Speed

1,500 2.9 Kn
2,000 4.2 Kn
2,500 5.4 Kn
2,800 5.8 Kn
3,000 6.0 Kn
3,200 6.2 Kn

I was able to increase the RPM to 4,200 before I checkened out and reduced the revs.

According to the manual maximum power for the 4JH3TE comes at 3,700 RPM.

I'm using a 3 blade MaxProp.

So my question now is .... does anyone think I'm underpitched on the prop or should I just be operating the engine at higher RPM's ?

I generally cruise at 2,800 RPM, but the above would suggest that 3,200 or even higher would be perfectly OK.

Also ... I managed to get some genuine turbowash from a Yanmar dealer. Seems that they now package it in 150ml packs (~$10), but the packaging instructions are entirely in Japanese. I'll have a go with this later.

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