2003-2008 39/40 Motor Yacht Burn Rate with 8.1 Gas

J

jmunro123

Member
Feb 2, 2008
370
Gran Bend, Great Lakes
Boat Info
2004 Sea Ray 390 Motor Yacht
Engines
8.1's
I was wondering if any MY owners could share the burn rate along with speed. I am particularly interested in hull speed with burn rate (close to 9MPH or 10MPH) and cruising speed.

I am getting close to an offer on one and my family want to travel this summer. We are a Great Lakes family and run about 60hours per year

updated August 27th 2010 - we purchased the 390 MY and the burn at 10MPH is 9gph.
 
Last edited:
I'm curious why you're asking this question- again.
Everyone's told you it's gonna drink fuel like a drunken sailor...whether you get .5, or .6 mpg, why the need to try to pin it down to an exact science?

Even if you're going to run around at hull speed, it's still gonna suck fuel, though not quite as bad.

Point is, this is not a boat for anyone concerned about fuel economy and range. It's at the bottom of the scale when it comes to economy of operation; except, perhaps, an old 40' Viking I saw once with gassers...

Sorry, guess you're not getting the answers you want to hear...
 
We run about 22MPH at 3400rpm with boat fully loaded with 3~5 people. Average about 33GPH at 3400rpm.
 
tobnpr said:
I'm curious why you're asking this question- again.
Everyone's told you it's gonna drink fuel like a drunken sailor...whether you get .5, or .6 mpg, why the need to try to pin it down to an exact science?

Even if you're going to run around at hull speed, it's still gonna suck fuel, though not quite as bad.

Point is, this is not a boat for anyone concerned about fuel economy and range. It's at the bottom of the scale when it comes to economy of operation; except, perhaps, an old 40' Viking I saw once with gassers...

Sorry, guess you're not getting the answers you want to hear...
Click to expand...

So based on your boat, what is the GPH at 9 MPH (hull speed) . Then what is the GPH at when on plan - and at what speed?
 
I have a friend that has these same boat and ran it from Stl to the Gulf at around the speeds you are discussing. I will ask him. He had a Meridian 381 and a S-R 320 prior.
 
jmunro123 said:
So based on your boat, what is the GPH at 9 MPH (hull speed) . Then what is the GPH at when on plan - and at what speed?
Click to expand...

It's not a comparison that would be of any value to you. Different hull, and diesel power. But since you asked, I get just under 1 nmpg at cruise (22 knots at around 22-25 gph at cruise). I don't have diesel Flo-Scans so I don't know fuel burn at hull speed, but it's definitely minimal. I can troll 6-8 knots all day and the fuel gauge barely moves.

In very broad, general terms- I think most would tell you that a 40 footer with adequate diesel power is going to give you a faster cruise speed, and something in the neighborhood of 50-75% better fuel economy. The 40 MY is obviously much heavier than a 40 express or DA- so it will require more hp and more fuel to run.

It may be that the boat you're looking at is a good fit for your family's needs. But, you need to weigh resale against that (as FW said). If the boat you're looking at has Smartcraft, why not ask the owner about the fuel burn?

I wasn't being a smarta**...just trying to be sure you're aware of the practical limitations and expense of running that particular boat/power setup. Many look at diesel power and estimate that the "payback" for the extra cost of diesel, based on the limited number of hours they run, isn't worthwhile. Nonetheless, they still freak out when they run 125 miles with the boat and then fork over the plastic for a $1,000.00 fill-up...

Also, consider that fuel prices are somewhat reduced from a year ago. If it goes back up to near $5 gallon at the fuel dock, is it going to affect your ability to use the boat the way you want?

Good luck, hope it works out for you.
 
jmunro123 said:
So based on your boat, what is the GPH at 9 MPH (hull speed) . Then what is the GPH at when on plan - and at what speed?
Click to expand...

It's not a comparison that would be of any value to you. Different hull, and diesel power. But since you asked, I get just under 1 nmpg at cruise (22 knots at around 22-25 gph at cruise). I don't have diesel Flo-Scans so I don't know fuel burn at hull speed, but it's definitely minimal. I can troll 6-8 knots all day and the fuel gauge barely moves.

In very broad, general terms- I think most would tell you that a 40 footer with adequate diesel power is going to give you a faster cruise speed, and something in the neighborhood of 50-75% better fuel economy. The 40 MY is obviously much heavier than a 40 express or DA- so it will require more hp and more fuel to run.

It may be that the boat you're looking at is a good fit for your family's needs. But, you need to weigh resale against that (as FW said). If the boat you're looking at has Smartcraft, why not ask the owner about the fuel burn?

I wasn't being a smarta**...just trying to be sure you're aware of the practical limitations and expense of running that particular boat/power setup. Many look at diesel power and estimate that the "payback" for the extra cost of diesel, based on the limited number of hours they run, isn't worthwhile. Nonetheless, they still freak out when they run 125 miles with the boat and then fork over the plastic for a $1,000.00 fill-up...

Also, consider that fuel prices are somewhat reduced from a year ago. If it goes back up to near $5 gallon at the fuel dock, is it going to affect your ability to use the boat the way you want?

'Course, I could buy much newer, or more boat today for the same $$ I paid for my 390 before the bottom fell out. But based on conversations with my surveyor, I first decided to go with diesel power for a 40 footer- then looked for a diesel boat that fit my budget.
Because I do most all the maintenance and repairs myself, I had no problem going "older" to get diesels...you might consider doing the same.

Good luck, hope it works out for you.
 
I don't think the resale value is much of an issue. Sure, there will be less value at resale but the buying price on a used SR with that set up will be low as well. Gassers in that style of boat on the Great Lakes are pretty common and the routine maintenance will be a lot less than diesels. You pay more at the pump but a lot less on other expenses. The major downside in my view will be low speed handling around a dock and fairly low speed cruising. I like to cruise at 26 knots and get to my destination, but this boat will be fine for someone with different tastes.
 
390 Gas Power Table.jpg I found the attached power table from an old article (http://www.boatingmag.com/gallery/photos/sea-ray-390-social-director?pnid=17519) I archived when researching the 40MY, may be what you are looking for. Power and Motor Yacht also has a test article on the 390 (http://www.powerandmotoryacht.com/boat-tests/sea-ray/0702searay390/) but the pictures including the engine test results table seem to have been removed.
 
Thanks Al, that is exactly what I was looking for. I did read that article but the chart was not viewable on my PC I guess. Anyways, thanks.
 
alnav said:
View attachment 9861 I found the attached power table from an old article (http://www.boatingmag.com/gallery/photos/sea-ray-390-social-director?pnid=17519) I archived when researching the 40MY, may be what you are looking for. Power and Motor Yacht also has a test article on the 390 (http://www.powerandmotoryacht.com/boat-tests/sea-ray/0702searay390/) but the pictures including the engine test results table seem to have been removed.
Click to expand...

Boating Magazine tests all their boats with an unpainted clean bottom, going down river with a strong wind at their back. That is my experience.
 
JV II said:
Boating Magazine tests all their boats with an unpainted clean bottom, going down river with a strong wind at their back. That is my experience.
Click to expand...

yes i think you are right, they always seem to be , but I was just looking for a comparison between displacement travel cost and planing travel costs. Looks like displacement uses about half the fuel for a given distance. Of course depriciation is a factor since more hours would be put on the boat.
 
JV II said:
Boating Magazine tests all their boats with an unpainted clean bottom, going down river with a strong wind at their back. That is my experience.
Click to expand...


Wrong................but close. Many boats are bottom painted as a part of their manufacture. The testing done by factory personnel for ad or sales literature and by boating mags is done with a painted bottom, but a lightly loaded boat. The boats are new, so the bottoms are clean. Figure their loading to be 2 youngish (not yet over weight) crew, 50 gal of fuel, no water, no waste, no gear the minimum safety gear on boats to be legal........a far cry from the way most of us load up our boats.
 
tobnpr said:
So my .5-.6 estimate was dead on...
Al, what are the numbers with the 425's ?
Click to expand...
I don't have all the data I've gathered handy but I do have a couple of important (to me) data points: Best hull speed of 8 knots burns 4 gallons per hour. 80% throttle cruise speed of 20 knots burns 23 gallons per hour.
 
jmunro123 said:
I was wondering if any MY owners could share the burn rate along with speed. I am particularly interested in hull speed with burn rate (close to 9MPH or 10MPH) and cruising speed.

I am getting close to an offer on one and my family want to travel this summer. We are a Great Lakes family and run about 60hours per year

updated August 27th 2010 - we purchased the 390 MY and the burn at 10MPH is 9gph.
Click to expand...

Soo,how do you like your 390?
 
Phillip E Johnson said:
Soo,how do you like your 390?
Click to expand...
Just sold my 390 MY this year, but I can tell you from the standpoint of being comfortable, it cannot be beat. The reason I sold mine was that I boat to be in the open air and sun and I could not take the closed in bridge with no ability to open the roof or windshield to get the boating experience I desired. You cannot beat the accomodations on this boat if you are okay with being closed in while operating it. I don't believe you buy any boat like this for efficiency!
Rob
 
Robf said:
Just sold my 390 MY this year, but I can tell you from the standpoint of being comfortable, it cannot be beat. The reason I sold mine was that I boat to be in the open air and sun and I could not take the closed in bridge with no ability to open the roof or windshield to get the boating experience I desired. You cannot beat the accomodations on this boat if you are okay with being closed in while operating it. I don't believe you buy any boat like this for efficiency!
Rob
Click to expand...

That did occur to me, limited open air exposure! I suppose thats a trade off for the air conditioned helm area. How did the 8.1's perform for you with a boat of that size?
 
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