I've been waiting to post this one on it's own thread:
The best 450 Euros I’ve ever spent
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
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.
P.S.: Other related repairs
prior to discovering a solution:
1. Fuel tanks
scrubbed and new diesel
from a petrol station filled (not dockside)
2. New injectors
3. Complete engine service
5. Fuel 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