3860 Cruising speed

[toymites]

I've got 8.1 mercruisers in a 3860. Has anyone done any research on optimum cruising speed for best fuel economy?

 

[rommer]

Regal specs say 27MPH at 3500 RPM burning 33GPH

Fairly close to boattest's numbers....

RPM MPH Knots Total GPH MPG NMPG Range NM Range dBa
1000 6.4 5.6 4.5 1.42 1.24 320 278 71
1500 8.4 7.3 7.5 1.12 0.97 252 219 75
2000 9.6 8.3 11.3 0.85 0.74 191 166 76
2500 10.8 9.3 19.5 0.54 0.47 122 106 80
3000 18.9 16.4 26.6 0.71 0.62 160 139 86
3500 25.7 22.3 32.5 0.79 0.69 177 154 88
4000 31.7 27.6 43.6 0.73 0.63 164 142 87
4500 36.0 31.3 59.9 0.60 0.52 135 117 88
4900 37.5 32.6 66.1 0.57 0.49 127 111 89

 

[Gerry75]

With my 3860, with the 8.1 volvos, my cruising speed at 3500 rpm is a bit less than Regal specs, about 21 kn. I find it's my best rpm's for fuel burn.

 

[toymites]

Thanks all. I usually run the boat at 3500 rpm, just feels "right". Glad to know thats the sweet spot.

 

[dbh95]

I run my 2002 3860 with twin Merc 8.1 HO 420 horse at around 3500 and my speed is about 23-24 MPH