Uneven fuel consumption?

Aerobaticflyer

Aerobaticflyer

New Member
Mar 24, 2009
263
Bradenton, FL.
Boat Info
390 Sundancer 2005
Engines
Cummins 380's
Anyone else with a 2005 390 Dancer that sees fuel being consumed faster from the starboard tank than the port side? I know the genset draws from the starboard side but I haven't been running it that much and it's consumption wouldn't give me what I'm seeing. Unless my sensors are not accurate I show 1/3 of a tank still in the port side when the low fuel alarm goes off on the starboard side. I know I'm consuming equally as I usually have the engine syncronizer utilized and the gauges indicate equal consumption. Mine is a diesel boat FWIW but I don't think the tank size / shape is different from gas. My guess is that the starboard tank sensor is not calibrated properly but can't be sure unless I run that tank completely empty. The reason I think the port side is accurate is it seems to reflect the proper range and fuel remaining when I do the math for what I should have burned.

Any thoughts?:huh:
 
My sensors report a 1 gph higher burn rate on the port engine even though I have the starboard selected as the source for the generator. This has also been verified by the port tank taking on more than the starboard during refueling.
 
Re-calibrating the tank sensors on your smartcraft would be the first step. I bet that is your problem.
 
When you fill up, how much fuel do you have to add to each tank? That's the first question.
 
Could this be a prop issue. Do you get the same WOT on both mains?
 
In my case, the rpms are the same and the difference is not just the SmartCraft calibration as with both tanks set to equal at fill-up A, the port tank needs more fuel by fill-up B. My log is on board so I cannot give you exact figures.

Don
 
Is it a significant difference? I fought this with my boat. After verifying the data as you have, I got the prop charts for my boat and learned that they are tuned differently in order to compensate for the fact that one transmission runs in forward and one runs in reverse to get the counter-rotating props. The transmissions have different gear ratios in forward versus reverse.

I took my props to a local prop shop with a computerized prop tuning instrument. They measured the props. They were similar. I had them re-tuned to make the engines match better. Then, I had them re-tuned again to match the engines almost identically. Now, when I cruise and match RPMs, after a couple of hundred of gallons of gas pass through, they use the same amount of gas within a gallon! The SC, though under-estimating my Fuel consumption by about 10%, shows them as matched when the RPMs are matched.

I do not know if this info applies to your boat, but perhaps it does. Good luck.
 
In my case both engines show identical rpms and both tanks have taken almost exactly the same amount of fuel the three times I've filled up. With both tanks starting full and both taking the same amount to refill the issue has to be with the "system view" readings I would think and likely tank configuration / calibration related. Any prop issues would result in different amounts of fuel actually consumed. In my case the difference is the reading of how much fuel is remaining on board. This is my first "system view" boat as opposed to "smart craft" I had on my 300DA (which also gave me inaccurate fuel use issues) so I have some learning to do. The good news is that I most likely have more fuel remaining in my starboard tank than indicated....I just don't want to find out I'm wrong 50 miles out into the Gulf! :smt009
 
How about the fuel return valves from the engines and gen? You should be able to select which tank to dump returned fuel into. If you are returning fuel from two engines into one tank then that may be your issue.
 
OK. I think we have determined that it is simply a gas guage error. This is not uncommon at all. Before you re-callibrate the guages, consider what happened to me. I don't know if SV is the same as SC, but when I did it, I followed the steps in the manual"

Empty tank
Tell guage it's at zero
Put in 1/4 gas - tell it it's at 1/4
Put in another 1/4 - till it it's at 1/2....

I only did this to my Starboard tank because it was nearly empty due to sharing gas with the genny.

After several outings, as I was nearing the end of my usable fuel, I began to notice that the stbd guage always read full, 3/4, 1/2, or 1/4 and no points inbetween. At 1/4 the stbd engine quit! I was out of gas on that side (genny had used some, again). Since it was such a pain to callibrate, I gave up and restored the factory defaults.

Now, my port fuel guage comes off full well before the stbd. By the time they get near empty, they start to level out more. This is when they are burning out the same amount without any genny usage. It's not too bad. I've learned to live with it. I do keep a log of what the guages were reading when I fill the tanks, and how much I added to each side. If I had to, I could go back and use that to determine how much gas I actually had left based on the guage reading. Good Luck.
 
Unless I can find something useful in my System View manuals I may get a wooden pole "dipstick." :lol:

I guess gallons put in minus GPH times hours ran will give me a good estimate as long as the pick up is near the actual bottom of the tank.

Someday someone is going to invent an accurate gas gauge for boats and get rich. I'm thinking load cells the tanks are mounted on and using weight to calculate fuel. No tank penetrations other than pick up. C'mon engineers at Sea Ray. (I'm asking for 10% of all sales if you use my idea!) :smt038
 
I have the 8.1 Mercruisers and presumably the same fuel tanks. I'm pretty sure that the problem you're having is with the SmartCraft calibration. I checked w/ Sea Ray 2 years ago and it turns out that port tank holds 143 gal. and the starboard holds 135 gal.. As your SmartCraft is showing equal fuel consumption port and starboard and you add equal fuel to both tanks at fill-up you would get an early alarm on the starboard side especially if you ran your generator at all. Hope this helps.
 
Last edited:
Surprise390 said:
I have the 8.1 Mercruisers and presumably the same fuel tanks. I'm pretty sure that the problem you're having is with the SmartCraft calibration. I checked w/ Sea Ray 2 years ago and it turns out that port tank holds 143 gal. and the starboard holds 135 gal.. As your SmartCraft is showing equal fuel consumption port and starboard and you add equal fuel to both tanks at fill-up you would get an early alarm on the starboard side especially if you ran your generator at all. Hope this helps.
Click to expand...

Good info to have..thanks. I think my side to side discrepency is too extreme to be explained by just an 8 gallon capacity difference and the generator consumption but I agree, my problem likely is in the calibration. My 300DA had the same kind of issue. One day I ran about 43 miles on an "empty" tank. :smt101
 
Your boat is equipped with 6 liter engines that will "return" about 8 to 9 gallons of fuel per hour at curise speed. If your fuel valve is returning both engines to the same tank then you would be essentially adding 8 to 9 gallons to one tank per hour while using fuel in the other tank without replenishing it. That could be the issue. What are your valves set at now?
 
How accurate is Smartcraft in a diesel application?
How does it account for return fuel (since it does not have flow sensors) accurately?
 
bluebelly said:
Your boat is equipped with 6 liter engines that will "return" about 8 to 9 gallons of fuel per hour at curise speed. If your fuel valve is returning both engines to the same tank then you would be essentially adding 8 to 9 gallons to one tank per hour while using fuel in the other tank without replenishing it. That could be the issue. What are your valves set at now?
Click to expand...

Yikes.....now that could be a thought and I have to admit my ignorance being new to the diesel world. I knew fuel is returned to the tanks but I assumed port stayed with port and starboard with starboard. I did not know I had the option of selecting the destination of an engine's returning fuel. This is so? If it is why would someone want to send fuel back to someplace other than where it originated? Are there valves that are self explanatory I should look for? Sorry if I'm asking basic questions that are best answered in the manuals (which I'll check next time I'm on the boat).

Sound like an easy fix if all of this is the issue. :thumbsup:
 
After putting more thought this I believe that your boat may not have the crossover valves for the engines, but rather only for the generator. My 44 dancer has the crossover valves mounted under the cockpit sink and I remember now that they are only for the generator and not the engines. This still may be your issue, just that the generator is what is drawing from one tank and returning to another tank. The generator is capable of returning up to 1.5 to 2 gallons per hour.

Sorry if I gave you wrong info.
 
bluebelly said:
After putting more thought this I believe that your boat may not have the crossover valves for the engines, but rather only for the generator. My 44 dancer has the crossover valves mounted under the cockpit sink and I remember now that they are only for the generator and not the engines. This still may be your issue, just that the generator is what is drawing from one tank and returning to another tank. The generator is capable of returning up to 1.5 to 2 gallons per hour.

Sorry if I gave you wrong info.
Click to expand...

No problem.....I'll check into the generator fuel return. I don't believe I have been running the generator enough during my recent trips to allow for such a large fuel discrepency but still worth checking out. I'm thinking the generator burns about 2 gph at 50% load plus the return that could be going to the port tank instead of starboard.
 
As I rack my brain over this it occurs to me that if both tanks take equal amount of fuel to fill them it confirms that I am consuming equal amount from both sides. Therfore the issue can't be in valves, return fuel, etc. There are only two possible explanations as I see it:

1. My port tank is actually smaller than 135 gallons (the Smart View system says 130 gallons) or......

2. My fuel sensor does not reach the bottom of the tank thus displaying a false empty reading.

I'll have to see if the tank is stamped with it's capacity.

After running the boat this past weekend starting with full tanks (and didn't run the generator) my port gauge read 3/4 full and my starboard read 1/2. Frustrating because your range is limited to the smaller tank.:smt013
 
Gas gauges are an aid on a boat, but not gospel. You know that they burn about the same, and you know your usage. Keep track of what you have used and you will know what you have left. The guages can be used as a reminder.

After buying our boat, we traveled 4 days/700 miles to get it home. On day 3, we stopped 12 miles short on account of the guages. I took note of the fuel required to fill up versus the total capacity and put that info into my bag of tricks. 1 day later, we came into our local pass indicating double "E" and 0/0 on the digital guage, and stayed on a fast plane all the way home to our marina. When we filled up, we still had 30 gallons to go.

Other than being a little bit of nuisance, it's no big deal. Private airplanes are treated the same way. Never, ever trust the guages.
 
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