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Old 03-12-2017, 05:08 PM   #12
DavidM
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City: Litchfield, Ct
Join Date: Aug 2012
Posts: 6,785
Quote:
Originally Posted by bayview View Post
IMO cruising speed is the speed used by the seller to optomistically describe how fast the boat will go without being at WOT. On planning boats it is usually the highest rated RPM of the engine maker for other than brief operation. It is always an exaggeration IMO of reasonable operation if engine life and fuel use are considered important..


For example, Yanmar says that all of their engines can be run continuously at 200 rpm less than rated rpm/hp. To say that my 370 hp 6LY, a high output engine that makes 70 hp per liter, can be run at 55 hp per liter continuously is total BS. And it is even worse for their 80 hp per liter at 4,000 rpm BY engines.

You need to get down to about 40 hp per liter or 400 rpm less than wot for the engine to have any decent life.

David
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