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Old 13 July 2005, 17:59   #1
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Cruising speed?

When looking at performance figures for new boat packages most manufacurers give a cruising speed. How is this calculated?
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Old 13 July 2005, 18:13   #2
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Probably maximum speed minus 5 knots I reckon.
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Old 13 July 2005, 18:24   #3
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Though it might be connected to Engine RPM, like an economic speed where the engine isn't as stressed. Say 4000rpm?
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Old 13 July 2005, 18:28   #4
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That's what I reckon Andy.

to Richard B!
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Old 13 July 2005, 18:32   #5
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You reckon it's that scientific? Maybe, but then maybe not!
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Old 13 July 2005, 18:34   #6
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I'm not too sure about outboards but diesels are rated according to their design specification, eg. pleasure, commercial etc. This is typically given as x amount of hours at full throttle in a y time period and, also, an engine speed which can be maintained continuously. For my KAD 300, recommended max rpm -200rpm is the continuous use rating, which, I guess, is the max permissible cruising rpm.
I reckon that's still got to be stressing the engine a bit and I've settled on approx
-900rpm for a balance of performance against longevity for normal use and -500rpm for when I'm in a hurry. And then, of course, there will be those occasional blasts flat out just cos' I like it. However, I intend not to break it, ever.

For outboards, I reckon cruising at about the max torque rpm wouldn't be a bad thing.
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Old 14 July 2005, 04:52   #7
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is the 70 % of maximum rpm, is also the revolutions that the engine can be on for 24 hours as day ...

at least this is what the told me.. lol
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Old 14 July 2005, 06:42   #8
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If you aim for 3/4's of top speed you won't be far off.
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