Question for C-Dory Loopers

thataway":f9tlrobn said:
Taking the question Larry asked and Nick's: Here is Boat Test C Dory 25:

2500 RPM 8.8 MPH 7.7 Knots 1.9 Gallons per hour 446 Range.

This is light new boat....but at displacement speeds this would not be surprising.

If you drop it down to 1500 RPM, you will go 5.9 miles per hour and a range of 635 miles.
Click to expand...

Not sure these are real world numbers. We just completed a San Juan Island cruise covering about 90 miles, mostly at 2200 - 2400 RPM, ~5 - 7 knots, depending on wind and current. We started with a full tank and consumed 42 gallons of fuel measured on fill, which computes to about 2.14 NMPG or 2.46 statute MPG. We ran fast about 20% of time however, and we are very heavily loaded. Even if we had not run fast, a range of 400 - 600 miles, even asuming you drain the tank dry, seems to me to be unlikely. We would be going considerably less than 5.9 MPH at 1500 RPM!
 
Pat,
No question that the "boattiest.com" numbers are always going to be optimistic, with brand new boat, new engines, absolutely clean bottom, and maybe two people--little gear and water--maybe half a tank of fuel at the most.

The 5.9 miles per hour comes from the Boat Test.com site:

RPM1500 Miles/ hr:5.9, Knots 5.1, gal / hour: 0.9, Miles/gal: 6.6 5.7 Statute miles rang: 631 miles, Nautical miles range: 549 nautical miles.

On the other hand, your numbers are a bit lower than our overall mileage in AK--in 1200 miles, we averaged a little over 3 miles per gallon. Part displacement and part low planing speed--since we also were heavily loaded, plus had the smaller 130 hp Honda.

One difference is that we tried to time our traveling thru the passes either at slack water, or with the current. We were used to doing that with the sail boat, which was a 6 to 8 knot boat... We always put the dinghy on the roof--never towed it.
Just little things like that can make a difference.

However--with a current of 2 to 3 miles per hour pushing you, that can make a very significant increase of range when going at displacement speeds!
 
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