Re: [Amel Yacht Owners] RPM on Volvo TMD22A, again...!

dgoffaux <dgoffaux@...>

Hi Erick,

Thanks for the answer, you are right about the torque. Only, it still
seems strange to be so close to the maximum, as at maximum throttle, I
reach 2600 to 2700 rpm, and that gives a notch above 7 knots (not
exactly hull speed). Which means that I should cruise at 2000 to
2200, maximum, at maybe 6.5 knots. Does that sound right?

My previous boat had a Yanmar, somewhat faster reving, so this one
puzzles me.

Best regards,

Daniel Goffaux

--- In, "Erick MEJEAN" <maramu@h...>

Hi Daniel

You must consider two things when you look at an engine performance.
Power output and torque. Each engine has its own power curve and torque
Both don't follow the same pattern and don't have the same meaning.
With regards to the TMD 22 it reach its peak power of 57.4 KW at
4500 RPM,
but it reach its peak torque of 162 Nm at 2400 RPM.
At 4500 RPM the torque is down to 125 Nm.
While motoring you are more interested by torque than power as
regardless of
the power you will never achieve a higher speed than the hull speed.
Running an engine at its best torque does not make it labouring the
sea as
it is the time when the engine has the more strength.
The calculation of the propeller pitch takes into account all these
Changing the propeller pitch would be a big mistake as it will make
prop no longer adapted to the engine,transmission and hull specs.
Propeller companies are using extremely sophysticated software to
the size and pitch of a propeller given a boat specs.
The power will only help you to maintain a higher speed while
motoring in
choppy water or against the wind but the overall efficiency of your
will be lower.
You also need to consider the consumption. While running your engine
at 2500
RPM your consumption will be in the range of 7 L/h and you will
reach your
max hull speed. Running the engine at 3500 RPM will multiply your
consumption by almost two and your speed will remain the same. Which
basically a fuel autonomy divided by two........
What the engine does not like is to be run at the same RPM for
hours, which
never occur to a car engine. As such to prevent the turbo clogging
three hours you should push your engine to 3000 RPM for around 20
min to
eliminate the carbon residues. Eventhough you run your engine at
3500 RPM
for hours without changing the RPM sooner or later you may face this
clogging problem.
Hope this will answer your questions

With best regards


----Original Message Follows----
From: "dgoffaux" <dgoffaux@b...>
Subject: [Amel Yacht Owners] RPM on Volvo TMD22A, again...!
Date: Wed, 23 Apr 2003 20:50:03 -0000

So happy to have found this site! And to be able to find out how
others have solved various problems (few, actually, in my case) with
their Super Maramu! I purchased SM #135 last year in France (this is a
1995 model) had a good revision on all systems and crossed over to Ft
Lauderdale last December. 17 days from Gran Canary to Guadeloupe,
whithout pushing, the fishing was too good!

One thing I noticed at purchase time was that the engine, in gear,
will not go over 2700 rpm. The Volvo manual indicates a max. speed of
over 4000 rpm for the turbo version. The engine runs nicely, without
smoking and has about 2000 h. now.

The Volvo dealer in Guadeloupe said that they knew about Amel habit to
reduce RPM with the adjustment of the Max prop, a procedure whith
which they totally disagree! They recommend, at next haulout, to
adjust the Max prop as to obtain about 3,400 rpm with the engine in
gear (in neutral there is no problem to rev up).

In France, I also had the turbo dismantled and cleaned, as it was
found full of soot.

1. What is the normal max rpm for the Volvo, as per Amel, and/or as
per Volvo?
2. Presumably, if the pitch of the Max prop is to high, keeping the
engine "labouring", it will induce sooting and will clog the turbo,
especially if indeed it only starts to pump at 2500 rpm or there
about. This may explain why - as I just read on various notes on this
site- one needs to rev up to maximum revolution for a few minutes
every so often. Why not, instead, have the engine running at its
recommended speed?
3. Obviously, I can see why someone recommended to remove the turbo
and clean it every year. This does not seem right however. Nobody does
that on a car or industrial equipment for that matter.

Has anyone any suggestion? Should I leave my engine /Max-Prop as they
are, or should I make some adjustments?

One last question on the transmission: what sort of oil should we use,
it says on it ATF (Automatic Transmission Fluid) but what kind? There
are now 4 different Dextron type fluid oils, does it matter which one?

I would be gratefull if someone could shed some light on those issues.
Good sailing to all.

Daniel Goffaux
On "Passion"

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