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From: David&Joan (no email)
Date: Sun Oct 02 2005 - 13:46:36 EDT
As others have said, why bother. Most turbocharged diesels develop no boost
until over 1,800 rpm. Below this rpm it is as if there is no turbo. I assume
that you have a semi-displacement boat with a high output diesel and want to
cruise at displacement speeds where you will be running at or below this
rpm.
A good example is our new Mainship 34 with a 5.2 liter 370 hp Yanmar. That
engine will drive the boat to 18+ kts at WOT, 30 lbs of boost at 3.400 rpm,.
But it will cruise at 7.5 kts at 1,400-1,500 rpm at zero boost while putting
out 50 hp.
At the later conditions this engine is operating very similarly to the
venerable Ford Lehman 120 which has a similar displacement. If the Lehman
could get 10,000+ hours before rebuild, why can't the Yanmar at the same
conditions? To be sure, I will run her at high rpm for a few minutes after
each low speed cruise. I will do this to avoid any cylinder wall glaze and
blow out any carbon that may have started to deposit in the injection elbow.
This engine does have an exhaust system with almost double the diameter of
the Lehman and therefore might be more prone to carbon buildup at low speed.
I am also curious as to what "extra parts" other posters say they carry when
operating at lightly loaded conditions and why? It seems that any potential
problems with low speed operation are all internal.
David
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