Fuel Consumption Question Silverton 31

[derf]

I am consider purchasing a 1986 Silverton 31 Convertible aproximately 12000 lbs powered by twin vortec EFI 325 Hp and Bravo outdrives. Does anyone have a rough idea of fuel consumtion when operating on plane and when in displacement mode. Any rough guesses from similar boats will help. Thanks

[charmc]

Not exactly equal, but this is from a recent test of a newer Silverton 33' flying bridge convertible similar to yours. The boat is 16,000 lbs and engines are a bit more powerful than yours. A good guesstimate would have your boat getting 20-25% better mileage.

RPM MPH/KTS GPH MPG/NMPG SM RANGE NM RANGE Db TRIM°
1000 5.8/5.0 1.8 3.19/2.78 575 500 66 0.5
1500 7.9/6.8 3.0 2.62/2.28 471 410 73 0.5
2000 10.9/9.4 6.2 1.75/1.52 315 274 77 2.0
2500 12.4/10.7 11.8 1.05/0.91 188 164 82 4.5
3000 13.4/11.7 19.2 0.70/0.61 126 109 83 7.0
3500 19.4/16.6 27.8 0.69/0.60 124 108 85 10.0
4000 23.2/20.2 36.2 0.64/0.56 115 100 85 7.0
4500 31.1/27.0 44.2 0.70/0.61 127 110 91 6.0
5000 33.4/29.0 48.2 0.69/0.60 125 108 92 5.0
5400 35.6/31.0 50.8 0.70/0.61 126 119 92 4.0

[RockLaker]

Again, not the same boat but could help compare, my uncle had a 1990 34' Silverton Express Cruiser with twin 454s. Back in the day when it was new he said at WOT it got 1 mpg per engine. I know that's not proper fuel talk for boats, but the boat did about 40-43 knots at WOT. By the way, that's going by 4.54 litres in an imperial gallon.




RL.