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Old 09-11-2012, 03:24 PM   #11
Nomad Willy
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City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 14,929
I assume you have a Flow Scan or equivalent.
Under propped 100rpm and anything up to that I think is fine. I assume your rated rpm is 2500. What is it?
Looks like at 8.9 knots your'e at 50% load. A little over 2300 your'e at 75% load. That's where Steve DeAntonio says we should operate 75% of the time. And also I see that at about 80% of rpm your'e at about 50% load. I think I predicted that. I also see that at a bit over 6 knots your'e burning the same as my Willard even at that speed.
These numbers say that over propping shouldn't show a meaningful gain.
I also suspect that these numbers should be very close to the same for most Perkins and Lehman engines.
I think it also says that at 1600rpm this engine should be making 34hp. Assuming power output is directly proportional to fuel consumed as a percentage of maximum burnable. Does anybody else good (better) w numbers figure anything different? I'm glad you posted those numbers BH. Much can be read into the results.
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