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YANMAR 4JH3TE Slow throttle response when hot

Aug 9, 2019
12
Hunter 460 Maryland
On my last two 8-10 hour passages when I started heading in to the dock I noticed the engine RPMs took 10 or more seconds to respond to lever commands. Even more so for reverse than forward. Made for a dicey docking evolution. While running, the engine goes into reverse or forward immediately, I can hear and feel the clutch and see the water start moving. But when I go to throttle up, there is a 10 or more second delay until the engine ramps up to the RPM. So I clutch in, wait couple of seconds, move the throttle to 1800-2000 rpms and nothing for 10 seconds, then it speeds right up to the rpm's When not in gear, the engine responds fine to throttle commands.

When first leaving dock (engine @ 140 degrees) there is plenty of throttle response and no issues.

- I've checked the throttle cable and linkages and all appear adjusted properly.
- 25 hours since fuel and oil filter service. Sight glasses are clear, no bubbles and no leaks.
- Air cleaner is new at 25 hours.
- Turbo vanes are clean, exhaust elbow is not blocked.
- A little whitish, blue smoke at startup, but not burning any oil and the smoke clears after less than 15 minutes.
- Temps appear normal in the 160-185 range.

Thoughts?
 
Feb 21, 2013
1,234
Hunter 46 Point Richmond, CA
Aug 9, 2019
12
Hunter 460 Maryland
Thanks. I never scoff at the obvious. However, first thing I checked was fuel. I also read both of those threads and worked my way through the obvious items easy to hard.

Clear, clean and new filters bled out.

Engine starts and runs right up when it's cold. Runs right up when it's hot and in neutral. Put it in gear when cold and I get the expected throttle response. Go to do it when the engine is hot after running for 8-10 hours and there's a solid 10 second delay.
 
May 7, 2012
782
Hunter e33 Maple Bay, BC
On my last two 8-10 hour passages when I started heading in to the dock I noticed the engine RPMs took 10 or more seconds to respond to lever commands.
Certainly not a mechanic here, but when you refer to “lever” commands are these carried out at the cockpit throttle lever or the control lever at the engine? If not the latter, maybe try a change of engine speed with the control lever at the engine to determine if the fault lies in the engine itself or the throttle cable system. Also is there any lag in time when you decrease the engine speed when the engine is hot or is it what you would normally expect?
 
Aug 9, 2019
12
Hunter 460 Maryland
Crew was manning the lever while I was watching the engine linkage. The linkage actuates fine, but the engine response is slow. Decreasing engine speed seems normal and responsive.
 
Aug 9, 2019
12
Hunter 460 Maryland
Another thread on the subject with solutions posted: Throttle lag on Hylas 54 4JH3-DTE
Thanks for the new thread. I hadn't seen that one. I had a theory that maybe the prop was the issue. I had divers come out and check it, found a little fouled but nothing that should have caused this.

Interesting in that link that no one had a smoking gun. Some of the injection pump rebuilds went well while others not so well?

I'll sojourn on today and see how it goes. Today is mostly bridges and a lock, so it's gonna be a slow day anyhow. May need another day of troubleshooting.

Thanks again Sail SFBay for posting that link.
 
Aug 9, 2019
12
Hunter 460 Maryland
Wanted to check to be sure it wasn’t caused by overloading. I had divers out, found some fouling on the prop (few barnacles and some monofilament line). After cleaning, speed was much improved and cruised along great through the day. Leaving the dock in morning had no lag at all.

Still had the lag after running at steady rpms for a few hours. It’s definitely heat related. 2700 rpms for three hours, engine water temp 180 degrees (confirmed with heat gun). When I got about 20 minutes from the dock tested backing bells and sure enough, there was the lag of 10 seconds, also noticed maybe the rpms were a hundred or so lower than 750 when clutched in both forward and reverse. I tried opening the side door to get some cooler air in the engine compartment meant and ran at 1200 rpms for 10-15 minutes over to the dock and everything was back to normal.

So, definitely heat related. I’ll have to investigate the fuel return line to ensure enough fuel flow cooling to the injection pump.

180 cooling water temp seems perfect, but maybe the oil cooler is running hotter, possibly. I’ll have to get the heat gun to shoot some temps and compare.

I can’t imagine a full rebuild of the injection pump is warranted. It’s more likely a small adjustment of something, mentioned in the HYLAS post, that gets done along with the rebuild.

I will keep searching.
 
Jun 15, 2012
537
Hunter 50 AC Greenport, NY
To absolutely make sure it is not your fuel system, I would feed engine from a new fuel line connected directly to the injection pump with a new inexpensive lift pump in line to a clean jerry can with fresh new fuel. After this test you will know for sure that the problem in in the engine and not the fuel feed. Next place I would look is the turbo. Have you cleaned the turbo with Yanmar's cleaner fluid?
 
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Jul 5, 2011
464
Oday 28 Madison, CT
You say 180 is normal running temp. Have you verified that from the manufacturer's specs? My Universal M12 is normal at 165. If I saw 180 I would be looking at my water pump impeller, the hose from it to the HE and for broken impeller parts in the hose or HE. Still, I imagine engine specs differ from one make and model to another.
 
Oct 26, 2010
1,089
Hunter 40.5 Beaufort, SC
Sounds alot like "turbo lag" to me. Does your turbo have a bypass relief that may be sticking open when its hot?
 
Oct 26, 2010
1,089
Hunter 40.5 Beaufort, SC
@SEMPERAVANTI41 - I would not conclude from the troubleshooting chart that you have that there is no bypass or blowoff valve. Almost all turbocharged engines have these since when you back off the throttle the boose pressure doesn't drop instantly.

Here is a link on what BOV/BPV does. My comment doesn't mean that is a turbolag problem but I wouldn't be so quick to dismiss it. I realy does sound like turbo lag and when something is getting hot it is changing inside the turbo or with the bypass valve. It makes sense that even when hot, there is lag when it is loaded and not some much when there is no load. Just an idea to keep in mind.

 
Jun 15, 2012
537
Hunter 50 AC Greenport, NY
smokey 73, my comment about a "bypass valve" comes from looking at a description and parts list from the manual showing a diagram of the actual turbo. The engine in my Hunter 50 is turbocharged and I did not remember seeing any plumbing that wold indicate a "bypass valve or wastegate".
My attachment was just about possible causes of the lag in power output from the Yanmar manual.
 
Oct 26, 2010
1,089
Hunter 40.5 Beaufort, SC
smokey 73, my comment about a "bypass valve" comes from looking at a description and parts list from the manual showing a diagram of the actual turbo. The engine in my Hunter 50 is turbocharged and I did not remember seeing any plumbing that wold indicate a "bypass valve or wastegate".
My attachment was just about possible causes of the lag in power output from the Yanmar manual.
Sorry @SEMPERAVANTI41 - I interpreted your reference to the table you posted as the source that there was no bypass valve rather than a parts list or diagram. I'm surprised there is no wastegate but then again anything is possible. Hope you get it sorted. Still sounds like turbo lag but I don't know why it would be only when hot unless something happens in the turbo when it gets hot?
 
Aug 9, 2019
12
Hunter 460 Maryland
To absolutely make sure it is not your fuel system, I would feed engine from a new fuel line connected directly to the injection pump with a new inexpensive lift pump in line to a clean jerry can with fresh new fuel. After this test you will know for sure that the problem in in the engine and not the fuel feed. Next place I would look is the turbo. Have you cleaned the turbo with Yanmar's cleaner fluid?
Did the turbo wash, a few times. Didn't make a difference. I've gone through the boat side of the fuel system. I know that it has good fuel.
 
Aug 9, 2019
12
Hunter 460 Maryland
Sounds alot like "turbo lag" to me. Does your turbo have a bypass relief that may be sticking open when its hot?
As stated above, I don't see a waste gate or bypass relief valve, neither on the engine or in the parts manual.
 
Aug 9, 2019
12
Hunter 460 Maryland
You say 180 is normal running temp. Have you verified that from the manufacturer's specs? My Universal M12 is normal at 165. If I saw 180 I would be looking at my water pump impeller, the hose from it to the HE and for broken impeller parts in the hose or HE. Still, I imagine engine specs differ from one make and model to another.
Thermostats start to open at 140 and are fully open at 160, so I would think that 180 is perfectly fine. Especially considering the Yanmar high temp alarm is at 205 degs F.

I did check the impeller and it was fine, however one or two vanes had some slight memory, so I swapped it out to be sure. Didn't make a difference in the temp or the throttle response.

I'm not ruling out the rest of the cooling system as of yet, at least not until I do another flush and punch all the different cooler tubes.
 
Aug 9, 2019
12
Hunter 460 Maryland
Sorry @SEMPERAVANTI41 - I interpreted your reference to the table you posted as the source that there was no bypass valve rather than a parts list or diagram. I'm surprised there is no wastegate but then again anything is possible. Hope you get it sorted. Still sounds like turbo lag but I don't know why it would be only when hot unless something happens in the turbo when it gets hot?
I'm not ruling out turbo lag just yet. After doing the wash and burning all the liquid out, I shut the engine down and tried to spin the compressor vanes by hand, or rather, by smallest finger I can get in that tiny turbo....The vanes did not spin freely like I expected, yet they spin, or at least appear to spin fine, when the engine is running. Other turbos I've worked on spin and spin and spin with just a little push. However, the exhaust is clear when the engine is hot, no black smoke at all. Still though, I have one more day to my destination of managing this slow throttle response and then the turbo is coming off and apart for a full turbine/compressor cleaning and inspection.
 
Jul 23, 2009
367
Beneteau 31 Oceanis Grand Lake, Oklahoma
Any chance that the fuel tank vent is blocked? After running for a long period of time a vacuum will be created in the tank creating fuel starvation. After the engine load is reduced or the engine is shut down air may slowly enter the tank releasing the vacuum. It appears heat related but it isn't.
I haven't read any of the links so forgive me if this was already covered.