380 Aft Cabin fuel range

HailDat

HailDat

New Member
Apr 8, 2021
6
St. Augustine, FL
Boat Info
Sea Ray 380 Aft Cabin
Engines
454 MAG MPI x2
I am closing on a 380 AC with Mercruiser MAG 454 MPIs and am wondering about the overall fuel range at different speeds. I know she's going to be quite thirsty but have had a hard time finding specific data on this.

Any owners out there with experience on this configuration with some real world data to share on fuel usage at WOT, slow cruising, and any points in between? Much appreciated!
 
HD, It all depends on operator, people on, gear, water chop, tide. It varies from day to day. Fuel usage at WOT, take 5 gal bucket and start bailing out the gas tank.
 
I serious, not like a car, there no way to measure mpg on boats consistently, it will vary as simple as type of bottom paint and it’s condition. Gas is the one thing you don’t want to measure as a boat owner, you really don’t.
 
You need to track it a bit on trips, tracking hour on engines as well as speed and on plane the whole time. Certainly would be at least 50gal per hour if not further north
 
As a fellow current gasser, I'll say this. Guests in the Bahamas with us on my other boats would occasionally "help" when we went to the fuel dock. "How much is fuel?" they would ponder.....as if it would matter. "99 cents" was always the reply. Where, and whom are you going to shop when at the bottom of the Exumas? Whatever you are driving, slow down if it hurts, and put it to the cruise if it doesn't, or something is chasing you. It is the one number you do not want to track, except to see when you need to stop again.
Try a plane. Fuel is cheaper, everything else isn't.
 
Thank you all for your replies.

I guess I should word my question a bit more specifically. I know that it will guzzle gas at WOT, and I know gas will be a huge expense if I drive it like I would've when I was 18.

But I'm really looking for an answer to a more practical question as to the range that I can hope to achieve (with a 300gal fuel capacity) at different operating levels. For instance, can you make the 170 statue miles between Carabelle, FL and Tarpon Springs, FL at a normal cruising speed?
 
HailDat said:
Thank you all for your replies.

I guess I should word my question a bit more specifically. I know that it will guzzle gas at WOT, and I know gas will be a huge expense if I drive it like I would've when I was 18.

But I'm really looking for an answer to a more practical question as to the range that I can hope to achieve (with a 300gal fuel capacity) at different operating levels. For instance, can you make the 170 statue miles between Carabelle, FL and Tarpon Springs, FL at a normal cruising speed?
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My dock mate has a 400 Sedan Bridge with the 7.4s. He burns 33 GPH at 3300 RPM getting 17 MPH average.
 
We go north each summer some times we make it to Alaska some times not. We run at 1200 to 1400 RPM most of the time a burn 1GPM or 6 to 7 gallons an hour. If we get in rough water we go 1900 RPM and burn 16 GPH at 9 knots. When things get rough, 5 footers we will run at 2500RPM and go maybe 12knots max. At that speed we are around 25 GPH When the 4 barrels open at 3400 RPM fuel consumption goes up very quickly. Fully loaded we can do 18 Knots and burn 55GPH. With 300 gallons we feel 200 Knots is a max safe distance. We have very accurate fuel use gauges and the closest we have ever run is 250 gallons. At that point you are looking at running on engine and going slow. I met someone who had same size boat with aft cabin not a SeaRay had 454s. He ran on one engine most of the time at 7 knots and felt he used 2/3 the fuel he would if he used both engines. I think he said he did 7 to 8 knots.
 
HailDat said:
Thank you all for your replies.

I guess I should word my question a bit more specifically. I know that it will guzzle gas at WOT, and I know gas will be a huge expense if I drive it like I would've when I was 18.

But I'm really looking for an answer to a more practical question as to the range that I can hope to achieve (with a 300gal fuel capacity) at different operating levels. For instance, can you make the 170 statue miles between Carabelle, FL and Tarpon Springs, FL at a normal cruising speed?
Click to expand...
My recommendation is test this out, run a short trip (1 hour, at best cruise), with full tanks, record your fuel flow, fill up, verify you burned what you expected. Then, calculate that out with 10-15% reserve, and see if it makes sense. On actual trip, start out at your best cocktail speed (4-5 knots?), then best cruise, and watch that fuel burn and speed, if it’s better than test, great, worse, recalculate. As you get within 50 miles, if you think you need to, slow down to conserve fuel. Also, verify you have tow coverage for 50 miles outside of carabelle (or Tarpon springs) and use it if needed!
 
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