Volvo D9s

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Driver06

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I am buying a Pearl 50 with twin Volvo D9s. Most of the time I am happy to run at 1000rev/min giving a peaceful 8 knots and economical 2.4litre/mile. I have never had these engines before. No doubt I should run them harder every so often to avoid clogged turbochargers, glazed cylinder liners etc. Could anybody suggest how frequently they should be run harder, for how long and what revs/min, please?
 
The figures were taken from the surveyor's sea trial. My current Azimut 43 with twin Cummins 425hp consumes a total of 2 litres per mile at 8 knots.
 
Brixham Bound said:
What boat and engines does 2.4 litres to a mile.
Click to expand...

Most do subject to how you drive them. At 8 knots is normal. I think you are mistaking LpNM to LpH (liters per hour).
To get a liter per mile, you take total liters per hours divided by the speed you are making.

Example so if you are consuming 100 lph at 25 knots you are doing 4 liter per nm.
If you are doing 100lph at 20 knots is 5 liter per nm.

A liter per nm is always the correct figure to say in regards to consumption.
 
Hi there……..and best wishes with the Pearl.?
Mine was the MBMY boat which was tested Jan 2007……..and I believe those figures.
At speeds up to about 9kts the boat was very economical at around 2 nm per gallon which is in line with what you’ve been told.
Of course it increases a lot when you get into semi-planning mode!
I‘ve just been looking through the MBMY test figures……but unfortunately they only start at 14kts.
I’m sure I’ve got some real-time data on low speed running in the old log books somewhere.

Afraid I’ve got no advice to offer on continual slow running of the engines.
 
Re massaging the rpm looking over your shoulder in terms of longevity.( hopefully not seeing smoke :) )

I understand the comments you make re bore scoring , glazing etc are mainly for older none common rail .
Some recent CR ( not sure if VP are in the group ) have sufficient electrotwackery to dial down the injectors fuel release as the rpms drops even at nearly tick over .If so they do not suffer from the trad issues that you raised .
Plus regular, or more regular oil changes because you are replenishing the vastly depleted additive package in the oil that low temp high hrs running does .

How ever having said that it’s all about heat , getting the optimal heat in the cylinders for the rings to expand to seal and indeed the fuel to burn correct and the injector cannuli ( multiple on CR ) to remain un clogged with soot etc .

Maybe spend the last hr at optimum rpm if you have ran them at 9 knots all day .
Bit late now but my view is buy a boat that fits intended purpose.Ie if it’s a planing boat = plane it .
If you don’t wanna raz around above 25 knots then buy a displacement boat in the first place .

Reminds me many years ago visiting the Sunseeker factory circa 2005 they had ( the then halo model ) a Pred 95 in .
The owner had commissioned it for a year off spending time with family cruising the Med with crew in a live aboard kinda way .
Rather than opt for the twin 2000 Hp on Anrnesons or indeed a triple he specced a pair of 300 Hp John Deeres .This is because the 10/13 knot D speed suited to intended usage and obviously room for bigger tanks , water makers etc so more autonomy , weeks between fill up in secluded bays rather than days , the std spec burning 1000 + L / h .

The JD s were run at optimal rpms and thus rocked up 1000 s of uneventful hrs in the year .Plenty of crew night passages.
Wake up at another island and when in a marina still got the stunning looks etc .

No worriers about guesstimating the D speed vs planing speed of the 2000 Hp V16 MTUs .
 
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Thanks for the useful comments. In fact I need a planing boat for those less frequent times when I am in a hurry, especially when I dont want to take 12 hours plus to cover 100 miles. I wonder if Volvo Paul has seen this thread......
 
Hi, share this "expertise" idea which is a common way to operate a marine diesel that is not a common rail.

The D 9 575 hp Volvo penta can be run at low rpms but it will eventually begin to clog up with soot in the exhuast system. The D 9 575 hp Volvo penta has a max rpm's of 2500. If you run it around 1000 you should be fine. Mnay fish boats troll for hours at even lower rpm's, but you want to run the engine hard for about 15-20 min after a few hours of trolling. That would be usign the engine at about 2300 rpm's for at least 10 min and maybe up to a half hour to blow out all the carbon bits.

Also just before shut down, in neutral, run the engine up to max throttle for just a second, then while the enigne is slowing down push the shut down. This is another trick people use to blow out the last of the carbon bits and keep the enigne clean inside.
https://www.justanswer.com/boat/41fp9-harm-run-50-foot-boat-volvo-penta-d9-575.html

NBs
 
Thanks for the reply, Vovo Paul. Can you let me have your opinion of what frquency of fast running would compensate for the ill effects of slow running, please?
 
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