2015 21EC speed RPM data

[Pilotnavigator]

just returned from a ride.wind was light. We had three adults on board with a quarter tank of fuel.
RPM. Speed Knots
1200. 3.8
1500. 4.5
1700. 5.05
1800. 5.25
1900. 5.50
2000. 5.70
2200. 6.00

Engine is the Volvo and I do. Or have info on the prop size.

 

[Handy]

I took my 21 out for afew hrs last week on Lake Erie , it's a slow but very enjoyable ride. Your rpm and speed match what I was getting as well.

 

[tlkenyon]

Here are the speed vs RPM data from a Classic 21.

 

[baz]

What was the fuel burn at 6 Knots ? Thanks... 🙂

 

[SGIDAVE]

What was the fuel burn at 6 Knots ? Thanks... 🙂

On my Yanmar 3YM that would equate to approx 1.5-2 QUARTS/HR.

dave

 

[baz]

What was the fuel burn at 6 Knots ? Thanks... 🙂

On my Yanmar 3YM that would equate to approx 1.5-2 QUARTS/HR.

dave

So with the 18 gal fuel tank that would give you a max of some 36 hours using the 2 quarts/hr... and at 6 knots/6.9 mph gives you a max range of some 250 miles. Using the 1.5 quarts/hr you get 48 hrs and a max range of some 331 miles. Very economical... 😎

 

[SGIDAVE]

What was the fuel burn at 6 Knots ? Thanks... 🙂

On my Yanmar 3YM that would equate to approx 1.5-2 QUARTS/HR.

dave

So with the 18 gal fuel tank that would give you a max of some 36 hours using the 2 quarts/hr... and at 6 knots/6.9 mph gives you a max range of some 250 miles. Using the 1.5 quarts/hr you get 48 hrs and a max range of some 331 miles. Very economical... 😎

Hello Barry,

Hold on for a minute. The numbers given so far are, to me, "test tank" numbers. That means my 21EC burn 1.5-2 qts/hr under ideal conditions. If you operated only on a lake without tidal influence or other significant current your fuel consumption would more closely match the figures stated.

I routinely run 80-120 miles before refueling. I meticulously record my engine and distance metrics. I average 10.5-11 mgp OVERALL most of the time. I have had fill-ups where my average was 12 mpg. As with driving a car, periods spent idling, running WOT briefly for engine health, and/or traveling AGAINST a 2-3 kt tidal current all reduce the overall mpg or increase the GPH figures. This yields gph AVERAGing 0.55-0.65 gph. I run at 2000 rpm normal cruise. If fighting head current, I may increase to 22-2300. "Fast" cruise (an oxymoron when speaking about a 21EC) for me is 2500. I'm running Acme #224 which is the more aggressive prop and my WOT rpm are 32-3300, maybe slightly higher in freshwater. I trailer my boat and presently have a 'bare' bottom - no bottom paint.

Given the above, I would consider the 21EC "range" to be more like 150 miles which will leave AT LEAST 3 gallons reserve, and, if you KNEW you where journeying that far, you would keep your speed more economical, which would leave a reserve more like 5-6 gallons which gets you closer to the 1/3 cubed rule. It would not be difficult to carry an extra 5 gallon jug or two of fuel if nec'y.

That's just my experience with the Yanmar 3YM powered 21EC. YMMV 😉

dave

 

[baz]

Dave: Thanks... Yes, I do understand the variations you've mentioned, and thanks for adding some 'reality' to my posted range numbers. 🙂