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Props - RPM's and Cruising Speed
On Fri, 28 May 2004 13:54:40 GMT, wrote:
I have a 30' Sea Ray Weekender with straight, 260HP, 5.7L inboards.
Currently, the boat cruises at about 20kts at 3,100 RPM's. At this
speed, I get reasonable fuel economy, because it's not until about
3,200 RPM's that the secondaries join the party and start tapping the
keg, if you will.
Max RPM on the boat is 4,100, at a speed of around 30kts. I very,
very rarely operate at this speed, and when I do, it's usually for
less than a minute.
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Your wide open throttle (WOT) RPM of 4,100 is already a bit on the low
side which means it would be a mistake to go to more agressive props.
Normal cruising speed for that engine is 3200 to 3400 RPM so you are
right where you should be in that respect. The real problem is that
you are slightly under powered for a boat of that size and weight. If
you are happy running at 3100/20 kts, I'd leave everything alone. For
more speed just figure on burning more fuel at 3200 to 3400. I have
the same engine on a relatively heavy 24 footer and run it at 3400 all
the time, sea conditions permitting.
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