Gas consumption on a 320 DA

[srdancer90]

Just ran out to West Hampton from Bay port/patchogue River burned 50 gal each side, 2 hours total. Can this be possible? I have a 2004 320 with 5.7 350 mag mie 300 hp each.

 

[skolbe]

At around 3600 RPM's my Smartcraft shows around 24 gph. So two hours 50 gallons.

 

[Two Peas]

But he said 50 gallons per side... Did he really burn 100 gallons?

 

[Sundancer]

WOT could burn 30 gallons per hour, times 2 hours and 2 engines would equal about 120 gallons. I'd say 100 gallons is probably pretty good. I don't know how far he went, if there were any winds or currents or what the load was. Since he only used 25 gallons an hour per engine, that seems within reason. Probably about a mile per gallon?

 

[Sundancer]

I thought the old rule of thumb was that you could burn 10% of your horsepower rating in gallons? So a 330 hp 454 Magnum could burn 33 gallons per hour? If that were the case, then he COULD burn 30 gallons per hour at WOT. Backing down to cruise rpm's might lower that to 25 per hour. As mentioned, that seems reasonable? Shoot, if there was someone else on here tonight........ Where is that cricket sound again???

 

[srdancer90]

Thanks for all the info. I had 4 people on board, both tanks were full, and I ran about one (1) hour each way about 3500 rpm. ( some times I had to pick up RPM , other times I slowed down.) The starboard side had 98 gal and the return showed 56, the port had 100 and showed 52.( when the trip was done.) My friends say that the boat should burn 30 gal per hour total, I read the Sea Ray report on the 320 and it said that 26.5 gph at 3600 (1/3 a tank on the sea trial, no water and two people on board.) but I am not sure if that was for each engine or for the combined total of two (2) engines. I disconnected the fuel leads and did an ohm meter reading and the starboard side read 80 ohms, 61 ohms is 3/4 tank 91 is half a tank. Called Mercruiser and did a recalibration of the smart craft gauges, no change in the readings.The next thing to do is eithor stick the tank and measure the gas available or fill the tank and see how much is needed.The issue is that when the boat was on blocks the starboard side read 35 gal, and the port side read 15 gal. I filled the starboard side with 40 gal and it read 98 on the digital smart craft, 60 gal on the port and it read 101. Future response is well accepted. Thanks for all the feed back.

 

[skolbe]

If your are relying on your fuel gauges after the boat has been sitting - then I would stop - gauges are a little unreliable - Fill the tanks all the way before your next run - the boat runs more efficient over 3600 rpms. But you should be burning around 12 an hour per engine on plane. Then refill your tank to the top and then measure fuel consumption.

 

[tdschafer]

Hey Joe,
You forgot to mention the superchargers on your motors!!!! LOL :grin::smt043:grin: Todd

 

[MattH]

I have had my '06 320 six months now, and I 'm still learning alot...I am keeping pretty close notes on fuel burn...my boat burns 22-24 gph total at 3600-3700 rpms...speed will vary depending on the number of passengers, fuel quantity and fresh water on board. 100 gallons in 2 hours seems excessive.

 

[Miller]

I have had the biggest problem with my '07 gas gauges with improper readings. I have had the senders replaced twice, the system reset, etc. Finally I think the problem has been solved by the last set of senders being replaced last week. My gauge read 3/4 full and when I pumped 90 gallons in, I knew I was completely messed up. I had the dealership do all the work since it was covered under warranty.

 

[srdancer90]

Tod the only thing super charged on this dancer is the money on gas. Your boat looks great, Hey by the way did you leave your gas caps open for me? I'm going to invest in a mega straw. Only kidding. My other friend who has a Wellcraft (we do allow non Sea Ray owners at our marina, it's difficult but we must give a little Leeway.) says that the amout of gas used was excessive it was 100 gal for a total of two(2) hours one(1) going and one(1) returning. Seems not possible, however I will fill up this coming weekend, and see what will take to tip off the tanks. The only other option is to only go to Watch Hill a 1500 RPM. "A slow boat to China"
2004 320 Dancer T 350 Mags
"Summer Wind"

 

[melida]

Hi all
Just looked to Searay site for 2004 320 specs.
It has 200 gallons of fuel tanks. So 100 for each engine.
According your's consumption 24 gallons/hour you have 4 hour/95-100miles range isn't it ?
If my math doesn't fool me why you(most of 320 gas owners) don't choose diesel engine?
Best regards.
Melida
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[Hampton]

100 gallons in 2 hours is too much, but I don't think you burned that much. My gauges go to zero about 30 gallons before empty - yours sound like they go to zero more quickly. Recal will probably not help. My guess is that it is a matter of the way the tanks are installed and how the probes sit in the tanks.

Do as suggested above: Fill her up, load her up, and take her out for a cruise. Note time, RPMs, speed, distance. Fill it back up and this will give you an idea of how accurate your fuel burn indications are.

 

[Alex F]

Just ran out to West Hampton from Bay port/patchogue River burned 50 gal each side, 2 hours total. Can this be possible? I have a 2004 320 with 5.7 350 mag mie 300 hp each.

srdancer90,
It looks like you're getting closer to finding the cause of the issue, which seams to be the gauges reading, not the actual burn rate. Keep us posted after you do your test with fill up/cruise/fill up again.

Hi all​

Just looked to Searay site for 2004 320 specs.
It has 200 gallons of fuel tanks. So 100 for each engine.
According your's consumption 24 gallons/hour you have 4 hour/95-100miles range isn't it ?
If my math doesn't fool me why you(most of 320 gas owners) don't choose diesel engine?
Best regards.​

Melida

The issue is that his numbers are 40-50% OFF. According to boattest results 320 has cruising range of 170 miles. Using simply numbers to calculate the hours we have 200gal / 24gph(total for both sides) = 8.3hrs. Based on my experience 170miles is very realistic number. I had never cruised for 8hrs streight, so I can't tell you how close this number is to reality.​

 

[melida]

Alex,

Thanks for the explanation.

8 hour still came to me very low range since diesels are common in most European countries and mine also doin.

Does the diesel engine price difference wouldn't amortise in 2-3 years if you 100hours/year?

Also the cruising speed of a 320 with gas and diesel is just same or 1-2mph less.

I have lots of friends in my country have 300-320-340DA's and both twin inboard-I/O they consume 11-15-18 gallons/hour respectively(340has inboards and others I/O).

So giving more $40-50K initial price would amortised in 4-5years.

For example my buddy has 2007 320 with twin Volvo Penta D4-260DP I/O and burns at cruising totaly 55lt/hr=14,5 gallons and if it had twin gas would burn 24 gallons gas as you do.

So 55lt diesel x 1,925$/lt x 100 hours=10587 USD yearly
24gallons makes 91liters gas x 2,3625$/lt x 100 hours=21500USD (prices are belonging to my country)

21500-10587= 10913 let's say 11k USD yearly.
While a boat is a long term investment my friend could amortise and will make profit from fuel at 5th year.

This is the basic calculation of buying diesel engined boats in my country.

Does this apply to USA?

Best regards
Melida

 

[Alex F]

melida,

I have no doubts that 320 with diesels would be more economical, but I wouldn't want it with I/Os (I'm in brackish and occasinally in salt waters, so I wanted to stay away from corrosion or other maintenance issues with I/Os).

The short answer is the price of fuel difference between US and Europe. 1,925$/lt = approx $7.60 per gal. where I pay 50% less. I would say this kind of applies the same to the cars world. You don't see too many full size SUVs in Europe while here they're all over the road.

By looking at your numbers:
"So 55lt diesel x 1,925$/lt x 100 hours=10587 USD yearly" I can tell you that for about 80hrs (seasonal usage) I had spent just about $1850 last year. So, comparing to your estimate I'm 5 times ahead. Now if I add the initial price difference $40K-$50K there's no way anyone here would go for it. We're simply in different market here and let's not forget the cost of the service for diesels, which is much more $$$. Often we're questioning why people buy larger cruisers with GAS, especially older boats with engines free of bunch of sensers? There are times when it makes sense for handy folks with GAS engine work experience. When something goes wrong they know exactly whta to do, where to get the parts and it costs much less than dealing with diesels. I know few folks on the board that are in this situation and it makes sense to me.

 

[skibum]

So 55lt diesel x 1,925$/lt x 100 hours=10587 USD yearly
24gallons makes 91liters gas x 2,3625$/lt x 100 hours=21500USD (prices are belonging to my country)

21500-10587= 10913 let's say 11k USD yearly.
While a boat is a long term investment my friend could amortise and will make profit from fuel at 5th year.

$11k - $21.5K for 100 hours of boating? Yikes! :wow:

And to think, you guys are sitting on so much oil, you'll probably sink one day.

 

[trit21]

. Using simply numbers to calculate the hours we have 200gal / 24gph(total for both sides) = 8.3hrs. Based on my experience 170miles is very realistic number. I had never cruised for 8hrs streight, so I can't tell you how close this number is to reality.[/LEFT]

Lets not forget you can't use all 200 gallons and magically be at the pump for more fuel. This is they way I figure my consumption and run time. Also , keep in mind 24 GPH seems a little low to me but YMMV.

I burn approx. 30GPH at 27MPH. 27/30= .9 MPG. 200 gallons of fuel, use only 90% for travel purpose leave 180 gallons. Now with the many many inlets in FL there is never really a problem using this formula on calm days/nights. When weather is present, I have enough data on my boat in rough head seas/wind to know it will use more fuel and adjust accordingly and add a little more safety margin, but for arguments sake, let us these number for max range.

180 gallons, burning .9 MPG
180 x .9 =162 miles of travel
Traveling approx. 27MPH 162/27= 6 hours of run time on plane using basically the available fuel.

And that is pretty close to actual.

Now load the boat for a long trip,bring in seas and wind, and you go down from there.

 

[melida]

Alex,
You are both correct of corrosion, yearly hour and cost of fuel.
Different country different price/tax regulations.
My government sees the boat owners as a cow and sucks our milk.
Until this year boats are taxed by their hp. If I'd put Turkish flag I'd pay yearly 285*77=21945Liras=13715USD yearly motorized vehicle tax.
Therefore everyone put USA flag to their boats including me, register to Delaware and pay just 500USD yearly.
Best regards.
Melida

 

[Vince_nj1]

This is what you should be burning. As already mentioned, your fuel guages are probably not accurate. My port engine says 10 gallons at the dock and then when I get on plane it shoots up to 30 gallons. Not very accurate...

http://i388.photobucket.com/albums/oo329/Vince_nj1/Boat Technical/320BoatTest.jpg