This has been going on since August. I just posted a small volume in the Yanmar group.

This is what I wrote:

The litany of woe continues. I apologize for the long post but to avoid "have you tried" responses I'm including the full history here.

 

For those joining the saga midway through, I have a 1991 Jeanneau Sun Odyssey 44 with the original Yanmar 4JH-TE with an unknown number of hours but indications are the boat has not been used much. Everyone who has been aboard has marveled how well the engine runs.

 

I've owned the boat now for two years. I put a Flex-o-Fold prop on it before it first went back in the water in 2024 after much discussion with the manufacturer to make sure it was the correct prop.

 

Since then I have put about 200 hours on the engine and prop.

 

I had the injectors serviced and a compression test done a year ago. Compression was within spec. At that time, I could get 3600 RPMs without spewing black smoke.

 

Earlier this year in April the boat was put on the hard to have the swing keel repaired. It turned into an epic huge project that took much longer than expected. The boat sat on the hard for over three months.

 

The only changes made to the drive train were:

 

• I replaced the zinc on the Flex-o-fold.
• I added a zinc to the shaft.
• I added a shaft shark line cutter attachment and was careful about measuring the gap.

Nothing was done to the engine.

 

Immediately upon launch I noticed that the engine was smoking significantly more than it had been when the boat had been pulled out. It would also not turn more than 2950.

 

It took some weeks to get a mechanic to look at it and he immediately identified that the turbo had failed so given that he said there was no point to checking the injectors. Not that it is relevant to the current issue but he noticed that the oil cooler and circulating pump had failed and that all the hoses were in need to replacing. (New to diesels I had a "certified Yanmar mechanic" do a 1000 hour service ... and he charged me for a new circulating pump but did not install it ... and like an idiot I was so focused on the getting the boat up to Annapolis I failed to notice the hoses had not been replaced.)

 

It turns out the turbo and exhaust manifold on the engine were from a different model, a 4JH2-TE I think, as the failed turbo had a cooling line to it and the correct turbo does not.

 

I replaced the turbo with a factory new turbo and replaced the air hose from the turbo to the intake manifold.

 

I pulled the core form the exhaust manifold and dipped it. I pulled the exhaust manifold and dipped it as well. I painted it and plugged the coolant port that went to the incorrect turbo. Looking at the parts fiche there doesn't seem to be any need to replace the exhaust manifold as the only difference I can tell is the presence of the additional coolant port. Whoever did this moved over the original plate from the engine.

 

None of this made any difference. It still smoked more and still would not turn more than 2950 RPMs.

 

I had another mechanic come and check my work. I questioned whether the fuel injection pump should be rebuilt. He agreed.

 

We did another compression test. Same results. Good compression. (I don't have the numbers in front of me but they were all within the "acceptable" range stated in the manual.)

 

So the fuel injection pump was pulled and rebuilt. He tested the injectors and found that three had failed so he rebuilt the whole set.

 

He timed the rebuilt fuel injection pump using a degree wheel on the crank pulley because the timing mark on the flywheel was no visible.

 

Just to eliminate the possibility I asked him to scope the cylinders in case they were glazed. He showed me that you can still clearly see the cross hatch markings on the cylinder walls in each cylinder.

 

He also replaced the fuel filters and the valve seals for good measure.

 

Upon testing, it smokes much less now. He said it is "smoking the amount you'd expect from an engine of this era."

 

We ran it on a 2 gallon tank at the dock and then compared it to how it runs on fuel pulled from the tank. Nothing is visible in the racor. Smokes the same. (Since the boat arrived in Annapolis last year, I've run about three tanks through it and I always get fuel at Annapolis Landing Marina. I'm told they are meticulous about their fuel.)

 

On both tanks, in neutral it spins up to max RPMs easily which he said rules out any issue with the new turbo or exhaust. (I was wondering if the turbo might be DOA.) It does not spew black smoke in neutral.

 

He said if the turbo were not working it would not spin up past 1500 or so. (Is that correct?)

 

However, under load it STILL will not turn up over 2950 RPMs. It starts producing noticeable black smoke once it gets over 2600 RPMs.

 

The mechanic now does not seem to believe me that it used to turn up to 3600 and tells me that the prop has to be checked. "It's acting like it's overloaded, maybe too much prop."

 

It's a brand new prop as of August 2024. I recheck with Flex-o-fold to have them double check. I have it clearly in my notes I used to get 3500-3600 out of it. There's no vibration. If there were some major issue with the prop I'd expect to feel the boat shudder. On every other boat I've been on, bent props or shaft cause an obvious shudder.

 

Just to eliminate the possibility since other had mentioned it a couple of times, I pulled the exhaust elbow to check for any obstruction. There's a slight coating of soot maybe less than 1mm. The tube to the exhaust is clear and there is no visible obstruction in the exhaust. The exhaust elbow is new as of 2024.

 

I'm going to see about getting the boat in a sling when I can schedule someone who knows what they are doing to look at the prop and make sure something hasn't changed.

 

It's been suggested that maybe if the turbo has a waste gate (does this one?) maybe it's not opening correctly. How does one check the boost on this turbo?

 

One person recited a story of how sometimes thieves will replace expensive items with cheaper ones. Maybe someone stole the prop and replaced it with an incorrect one and I didn't notice when it went back in the water? Doubtful but after all this I'm starting to ponder extreme outliers.

 

So for the few who have made it this far, if this were your boat and you had done all of this, what would you check next?

 

I'm at a complete loss.