500 Cockpit Motoryacht Fuel Consumption

[Y2K996]

I am closing on a 1996 500 Cockpit Motoryacht at the end of this month in Charleston SC. I need to drive her back to Cortez FL and was wondering what kind of fuel consumption I can expect at both planing and hull speeds. I plan on cruising around 18 knots when I can. She has the 8.3L 6CTA 420HP Cummins diesels. I have heard 1.5MPG off plane but I don't know at what speed or RPM that would be. Any help would be greatly appreciated.

[Midnightsun]

Your off plane best consumption speed would be at hull speed which should be around 8knots which is where I assume that 1.5mpg figure is coming from. At 2600 rpm that engine should consume around 24 gph x 2 and would think you can get her up to 18 knots. Those figures should not be to far from reality IMHO.

Here is a great article. Skip to the conclusion at the end where it really sums up the difference between different scenarios. Hull speed is your friend if you want to travel economically. https://www.passagemaker.com/technical/feel-the-burn

[Y2K996]

Thank you for your reply. I found a BoatTest.com review of a 2001 504 with 450HP Cummins that was getting around a half a mile per gallon at cruising speeds. I have to bring my new boat from Charleston to Sarasota so I'm trying to get an idea of how much I'm looking at for fuel for the trip. My current boat gets 1MPG at cruising speed and 2.3MPG at hull speed. Looks like this new boat is going to cost a little more than I estimated but you only live once.

[five0clock]

I tried to PM you and it would not let me do it. You may want to PM before you buy that boat. If it is the same one I am thinking about it sank in NC. It sat for a year in NC and they couldn't sell it, and now it is in Charleston. If you need more information just PM me. I am sure they have changed the name, but the one I had, had a green awning over the back sliding door.

[Y2K996]

I saw the one you spoke of and it was listed by a Charleston broker but it was actually in NC. I didn't care for it and purchased a different one.