Fuel burn with twin QSB 480 vs twin QSC 500

[Thomas Riley]

I’m comparing a 2009 Sea Ray 44 flybridge with twin QSC 500 straight shaft with a 2009 meridian 441 flybridge with twin QSB 480 v-drive. Boat displacement and length are similar. I like to go fast and slow but from my research it seems that somewhere around hull speed or 700-900 rpm or 7-9 knots, the QSB’s don’t do any better than 1 or 2 mpg whereas the QSC’s maybe get 5-7 mpg. At higher RPM’s the burn is pretty flat and similar for both. I’m wondering if this is true and if so why. 

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[Tony Athens]

Instruments/gauges, or ?? is wrong.. The vessel with less weight, less windage and the best ‘bottom /running gear” will typically get the best MPG at hull speeds assuming all is in “ass new condition” ..Longer LWL’s will increase hull speed some in some cases and some round chine narrow “east coast designs” can be “slipperier” in some cases at speeds below 10 kts.. ……………………  The engine choice or straight shaft vs V-drive  is not the issue as both have the same shaft / prop system under the boat.

[Steve Lewis]

TR,

I think something is very incorrect with your numbers.  Our boat is similar in specification to the 44Sedan Bridge.  We are a little longer and a little wider but weigh in about the same, maybe heavier in cruise trim.  We have the 480CE(8.3 ltr) so the predecessor to the QSC500.  Our hull speed specs are 10mph burning 5gph @1140rpm.  That is 2 miles per gallon.  I find it very hard to believe that the 44SB does 5 miles per gallon.  5-7 gallons per hour is more believable to me for hull speed.  That translates to ~2mpg which should be very similar to the Meridian.  I would check those numbers again…….

I would look at those boats from a layout and livability perspective instead of “Which goes faster”.  I think the Meridian has a bit more interior volume.  Larger living spaces I believe.  Also you might compare space in the engine rooms which will directly translate to ease of maint and daily checks.  You might find one is better than the other in that respect.

 

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