Lack of Power on Yanmar 4JH4-HTE

[mcerdos]

Any feedback would be most welcome.

I’m am experiencing a loss of power in both forward and reverse. The engine will rev to 3000+ RPM in idle. But, when in gear, at full throttle I can only get about 1200 RPM.


So far I have:

• Replaced Vetus muffler and ensured no exhaust obstruction
• Replaced impeller on sea water pump – previous impeller was intact. Plenty of water flow. I checked the cooling system to ensure no overheating.
• Replace Racon fuel filters – fuel flow is normal.
• Transmission gear cable is working correctly

I plan to dive tomorrow to check folding prop for obstructions. I can turn the shaft by hand so I do not see this as an issue but if a folding blade is faulty perhaps this may cause some issue.


I have expereince one hot light and shut the engine off quickly. This was caused by the sea chest and was since fixed. Hense, replacement of Vetus muffler.

Any areas I should examine?

[DeepFrz]

There are a number of threads dealing with this, or similar, Yanmar engine. They have either been Turbo problems or HP fuel injection problems. All have had lengthy and costly diagnosis/repair situations. I would suggest you use the Google search facility and do a search of the site for these threads.

[sailorchic34]

The basics would be to check the air cleaner filter, the discharge elbow for clog exhaust, valve clearance, Turbo operation and fuel injectors / pump.

Of course lots of barnacles on the prop would cause that too. Was there black smoke or grey smoke out the exhaust when running under load?

[mcerdos]

There is no excessive amount of gray or black smoke under load.

At this point, I really hope the prop is fouled with barnacles. This is by far the easier fix. I will update after.

[Kenomac]

I've been waiting to post this one on it's own thread:

The best 450 Euros I’ve ever spent

Carmeron,

It's a miracle! Our Yanmar 4JH3-HTE revving problem is solved, and you won't believe the cause. You might want to check your prop.... really?

Following months and lots of Euros spent, we replaced our deceased turbo with a brand new unit a week ago, certain that the burned out, rusty, no pressure turbo with missing fan blades was causing our low revving problems. Over the past seven months we could only rev the 900 hour Yanmar to 1400 rpms giving us 30hp instead of the promised 100hp. Excited.. We tested the new turbo on a sea trial..... results: Same problem, only now I was 4,000 Euros poorer.... and damn…. Now we had thick black smoke coming from the exhaust whenever the engine was under load. As if things couldn’t get worse… a new, or rather returning issue had re-surfaced which the UK surveyor had diagnosed as a transmission problem, so while I was making plans to have the engine management system fuel pump shipped to Barcelona, I decided to have the boat hauled out to check the Max prop which I thought was the occasional source of a banging noise when the transmission was shifted from forward to reverse. I did this so that I would feel secure while "putting around" the island at 5 knots on a 54ft yacht... After all… I didn’t want the “just serviced” prop to fall off.

In desperation, we contacted the "best" local mechanic money can buy in Mahon, Menorca, (Santi form Nautic Center) who came over to listen to the banging prop. After revving the engine a few times in gear at the pontoon.... he diagnosed the issue to be the prop propeller pitch. Really? So earlier today I hauled out onto a lifting sling for 450 Euros (which included the mechanic and an assistant for three hours) while the expert and his assistant took apart the prop (the same prop an expensive UK knucklehead mechanic had serviced 8 months earlier). At this point, I was willing to try anything before spending another 4,000 Euros on a new fuel pump injector system.

The mechanic asked me a few questions regarding what I knew of boat speed at various rpm’s, I wrote 7 knots @ 2,000-2,200, 6 knots @ 1800-2000, & 5-5.5 knots @ 1400 rpm... That's all I wrote down for him, my Spanish is horrible. He then did some figuring with his Max prop literature and proclaimed "the pitch angle all wrong.” He re-assembled the prop with the new pitch angle based on vessel length, engine hp, my stats and his "intuition."

I wasn't very hopeful; it was kind of like watching a guy look for a place to dig a water well using a forked stick. They put the boat back in, I stepped on the accelerator and WOW! 3,700-3800 rpm’s under load!!! 9 knots in calm water!!! A miracle!!

All he did was change the pitch angle of the prop.

Here’s a brief history of what happened:

1. The Oyster 53 had a knocking noise when I had it surveyed at purchase.
2. The surveyor diagnosed knocking as a transmission problem.
3. Idiot mechanic serviced the Max prop whilst re commissioning was underway.
4. Departed the UK with vessel able to rev to 2,400 rpm’s which I thought was normal.
5. The knocking went away, but over the course of the next 1800 miles the engine began to rev slower and slower while underway, until it would only rev to 1400 rpm and make 5 knots headway max.
6. 1000 Euros spent on diagnostics… you name it…. It was done.
7. Turbo was removed in Menorca and diagnosed as totally destroyed, by overheating and carbon blockage.
8. New turbo installed… same problem only now we had dark black smoke.
9. Prop pitched changed from 18 degrees to 14 degrees. Problem solved!

It appears now that our poor engine was working way too hard trying to drive the faulty prop pitch; then the fuel management system continued to compensate by throwing more fuel on the fire, which in turn clogged up the turbo with carbon, leading to its ultimate demise. Kinda like driving one’s car around all the time in fifth gear, lugging the engine.

I’m just glad to have it all behind me now. The best 450 Euros I’ve ever spent.

Ken McCallum

P.S.: Other related repairs prior to discovering a solution:
1. Fuel tanks emptied, tanks scrubbed and new diesel from a petrol station filled (not dockside)
2. New injectors
3. Complete engine service
4. Compression check
5. Fuel pressure check
6. Oil pressure check
7. Engine would rev to 3,600 without a load
8. Turbo boost pressure check
9. Turbo rebuilt (which didn't work out) I eventually bought a new turbo

[hpeer]

I had same issue last summer. It occurred after I had some gunk in the fuel. I think it got into the fuel injection pump.

Long story short, sent pump to rebuilder. They found nothing wrong, but said it was dirty. $400.

Maybe the governor is stuck, but no user serviceable parts.

If you are gonna remove the pump yourself let me know. I'll share my pain and "holy crap" story with you.

[CAELESTIS]

I just went through this exact problem last month. If you have been operating the engine in an overpropped condition, or have run it many hours at lower RPM,your injectors could be carboned up. If this is a sudden problem, then you should have the injection pump removed and tested.

[hpeer]

Yeah, actually my problem was a bit different. I would hit 1,600 forward or reverse ...in gear or out.

[bstreep]

If you aren't getting black smoke while in gear, it's NOT a turbo problem. Turbo problems are stupid common (note to self: turbos do not belong on a sailboat... but we have one).

[emcmia]

Originally Posted by mcerdos

Any feedback would be most welcome.

I’m am experiencing a loss of power in both forward and reverse. The engine will rev to 3000+ RPM in idle. But, when in gear, at full throttle I can only get about 1200 RPM.


So far I have:

• Replaced Vetus muffler and ensured no exhaust obstruction
• Replaced impeller on sea water pump – previous impeller was intact. Plenty of water flow. I checked the cooling system to ensure no overheating.
• Replace Racon fuel filters – fuel flow is normal.
• Transmission gear cable is working correctly

I plan to dive tomorrow to check folding prop for obstructions. I can turn the shaft by hand so I do not see this as an issue but if a folding blade is faulty perhaps this may cause some issue.


I have expereince one hot light and shut the engine off quickly. This was caused by the sea chest and was since fixed. Hense, replacement of Vetus muffler.

Any areas I should examine?

I installed a pair of 56hp 4JH3e in my Privilege about 1,000 hrs ago and never had a problem until last October. Stbd engine would easily start and idle in and out of gear. However, soon as I put it under load it would max out at less than 2,000 rpm ( normal max 3,800). Changed out filters and even a transfer plump. Ultimately determined that the Teflon tape on the threads of the suction-side brass fittings had deteriorated, causing air to leak into the line when under heavy load. Disassembled manifold, recoated threads with Teflon paste, re-assembled and its been running "hot, straight and normal" ever since.
Renewing port engine fuel manifold next month.

[mcerdos]

Problem solved!
Thank you Kenomac for the detailed posting. I kept leaning toward a prop problem. Your posting made me stay leaning that way because of the similarities of the symptoms.

I dove to check the folding prop. All the blades moved and I had a little barnacle growth. I clean it all up and noticed an improvement. I went back down to reexamine since nothing mechanically seemed wrong with the engine. When moving one of the prop blades it felt a little different from the others. I hauled the boat and removed the prop. One of the bearings in the prop showed more wear than the others. All the bearings were replaced and the prop reattached. That was it! Runs like a charm. I easily reached 3500 rpm.

I guess the silver lining here is the engine has had every conceivable component checked and rechecked.

Thanks all for the suggestions and help!

[Kenomac]

Originally Posted by mcerdos

Problem solved!
Thank you Kenomac for the detailed posting. I kept leaning toward a prop problem. Your posting made me stay leaning that way because of the similarities of the symptoms.

Thanks all for the suggestions and help!

You're welcome, 'just glad I could help.