Turbo boosting question

Many thanks for the replies all, it's greatly appreciated.
I didn't really make it clear about the speed loss, I'll give a bit of background...
Bought the boat in November, on a sea trial it was pretty sluggish but otherwise seemed ok. The sluggishness was blamed on fouling, which seemed reasonable as it hadn't been out of the water for some time.
Anyway, very long story cut very short, the boat didn't manage a single trip without some sort of problem with the outdrive until it recently destroyed itself. It's now had a new outdrive fitted, the hull is clean enough to eat your dinner off, and it won't achieve more than 8-8.5knots.
We spoke to the owners of the boat recently who had it before the guy I bought it off, they're the ones that did all the work with swapping out the engine.
Apparently it was a fast boat, capable in excess of 20 knots (I can't obviously prove that) but I have pictures of the boat after the work was done motoring along at some obviously quite considerable speed.
Problem is, the guy we bought it off had severely neglected it and (again, long story short) we were royally ripped off with it.

I have no idea what prop is currently fitted, it may well be the wrong one.
The boat is currently with the engineer who fitted the new outdrive, he's currently investigating the prop to see if a smaller one will restore the power. It just didn't sound right to me about the boost being dependent on revs but maybe it is then as per the reply above.
I'll see how he gets on with changing the prop, if that cures it then great, if not I'll ask him to give up on it and I'll investigate the other options.
Either way I'll report back :)
Thanks again for the help

Chris
 
lynall said:
Pretty certain Murv had this out recently to fix the outdrive, so any fouling would have been seen.
Murv which marina are you at cuxton/elmhaven, as im just down from you and could always have a look, cant garuantee anything but looking is easy!
What size is the prop currently fitted?


Lynall
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That's extremely good of you, thank you.
Sh'es currently at Wateringbury with the engineer but will be returning to Cuxton, either in working order or not as per my reply above.
If the smaller prop doesn't cure it, I shall certainly be in touch to see if you can spare a few minutes at some point.
Thanks again,

Chris
 
Murv said:
I have a problem that our Fairline holiday fitted with a Lancing marine 140bhp 2.5TDI engine won't achieve more than 8 knots, it won't rev to over 2500 rpm when in drive although revs round freely to max revs in neutral.
According to Lancing marine, the turbo should run at max boost of 15psi but it's only charging to 2.5psi at 2,500rpm.
The engineer thinks that it may be over propped, and that if the prop was smaller, it would obviously rev higher, then reaching full boost.
But, I always thought full boost was obtained far lower down in the rev range when the engine was under load hence the problem being the turbo not charging rather than the prop being the wrong size which isn't allowing the turbo to hit full pressure.
Who's right?

Cheers,
Chris
Click to expand...

Chris,

Listen to your technician he is correct........................Appears that most posters offering advice are clueless.

Your turbocharger boost curve is a characteristic of your propeller demand curve.

Proper and I stress proper Ford Power Products FSD 425 TCM is 130 Hp @ 4,000 rpm. However Mike Bellamy took plain vanilla naturally aspirated FSD 425's and simply stuck a dry turbo on them claiming 140 hp. If you have one of these Lancing conversions rated speed is 3,500 rpm as Lancing only increased the fueling and did not change the governor droop spring on the Bosch VE pump. Most of NA conversions done by Lancing have no LDA on the VE pump which is pretty hopeless. This is no sexy common rail motor, as simple as a wheelbarrow. Post a pic of your installation.

#1 Test your high idle speed, you NEED to see a solid 3,900 rpm with calibrated tacho, no blipping just lift the throttle and hold it there to ensure governor stabilises.

#2 If motor fails to make high idle check out throttle linkage, the break back lever on the VE should be just working with the lever hard against the stop.

#3 Once you you are 100% certain engine can make high idle and WOT test confirms you are making just 2,500 rpm (calibrated tach remember) you are way way over propped.

Another case of 'propellers move boats, engines simply turn them'.

UNTIL you can make a healthy 3,600/3,700 rpm WOT with a clean bottom forget boot pressure, that is for the birds.

Apologise to your technician and at the same time remember he is not an engineer.

Good luck.
 
That's extremely interesting, thank you.
The rev counter isn't obviously calibrated, but just going by the installed one it easily maintains full revs at WOT in neutral but only manages just over half that (by rev counter and by the note of the engine)
I have some pics of the install, they're a little random as I was taking shots to post on a Transit forum to try and identify the engine used for servicing requirements so apologies foe their random nature.

EDIT: Let's try that again...

EDIT again: OK, so it appears I can no longer insert images, I'll try and see where I'm going wrong
 
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Finally...

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I can finally update this thread for the benefit of anybody that might be searching the forum for similar issues.
The problem was a multitude of things.

1) The turbo was damaged
2) The wrong injectors had been fitted at some point in the past
3) The charge air cooler had a slight weep which was leaking seawater into the inlet manifold. This revealed itself when it let go completely and filled the sump with water.
4) The leaking CAC had blocked the boost compensator pressure line, but not before it had caked the diaphragm with salt and crud and stopped it moving properly.

Now, I have 15psi boost at 3500rpm and the tacho flies right round off the clock. In fact, I'm going to need to take some readings with the optical tacho to make sure it's not over revving!
Nice that it pops straight up on the plane too :)
 
Murv said:
Thanks for that, there is no smoke or strange noises and the turbo appears to spin smoothly. The air filter is off and the plumbing appears ok, so I shall investigate the wastegate.

Cheers,
Chris
Click to expand...

Bit of a long shot but worth checking the hose from the air filter to the turbo (if it has one) I have seen these look ok from the outside but the inside delaminates and blocks air going in.
 
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