On my Meridian 490 PH, Cummins B5.9MTA, starboard is 330hp, port is factory reconditioned 315 hp, any ideas why SB Engine used 26 more gals over a 200 mile run? Only used the penny for 4 hrs. Any idea on fuel consumption rate for an On an 13.5 Jenny? Thanks!! Dick
SB Engine Uses 26 gal More Fuel
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The Other Gary
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The 315 and 330 are the same engine if the CPL numbers are the same. They were marketed under two different HP designations.
Check the info plate on the port forward corner of the engine.
It should say CPL 1970 with Bosch pump or CPL 1928 with Nippondenso pump. Both are marketed as 315/330 hp depending on whether they use flywheel HP or shaft HP
If so, the stbd. engine may have more wear, and need more fuel to operate.
Failing that I would look to the condition of your props, engine alignment etc. and tach. accuracy
Check the info plate on the port forward corner of the engine.
It should say CPL 1970 with Bosch pump or CPL 1928 with Nippondenso pump. Both are marketed as 315/330 hp depending on whether they use flywheel HP or shaft HP
If so, the stbd. engine may have more wear, and need more fuel to operate.
Failing that I would look to the condition of your props, engine alignment etc. and tach. accuracy
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North Baltic sea
Guru
Hi, four things for which consumption difference may be due to.
1. Injection nozzle, The expoer did not complete-Check opening pressure and spray form
2. Injection pump, offers too much food-Adjust the pump
3. Check the air supply, the filter and the channels.
4. Turbo problem, possibly carbon deposits, or check whether the shaft is free.
Point 1 and 2 require professional and specialty tools. Point 3 and 4, it is possible to check in early to keep the mess on your hands.
The other Gary told of the good points as well, the gearbox, the propeller and the shaft line really can bring the consumption differences as well.
I hope this could help ...
1. Injection nozzle, The expoer did not complete-Check opening pressure and spray form
2. Injection pump, offers too much food-Adjust the pump
3. Check the air supply, the filter and the channels.
4. Turbo problem, possibly carbon deposits, or check whether the shaft is free.
Point 1 and 2 require professional and specialty tools. Point 3 and 4, it is possible to check in early to keep the mess on your hands.
The other Gary told of the good points as well, the gearbox, the propeller and the shaft line really can bring the consumption differences as well.
I hope this could help ...
What are you basing that on? How did you calculate the usage and difference?
If you are running your engine by matching the rpm then the difference may be attributed to the difference in your props demanding different hp port and stb to reach the same rpm - pretty typical on many boats. If you have calibrated fuel flow gages or have boost or EGT gages then you can likely prove this in real time.
a diesel genset will typically use about 0.1gph per KW produced. Often I see folks with your style boat cruising with the genset while using between 5,000 and 7,000 watts or less so that would be between 0.5 and 0.7 gph use at those loads.
FWIW - most of the 490 Meridians came with 12.5 KW gensets.
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MYTraveler
Guru
If you traveled that 200 miles at 8 knots, then the 26 extra gallons were consumed over 25 hours, or about 1 gph. My engines never have that large a discrepancy (at least not when both are engaged). In fact my engines' total consumption are within 1/2 %, with the engine that drives the stabilizer pump consuming the extra fuel. That extra 1 gph that your engines are burning is too large to be explained by normal variation between engines, etc.
Logically, it must be either that the loads are significantly different (as could be the case if a prop was damaged, etc.) or that your measurements are wrong. If you are confident in the measurements, I would focus on load, and disregard the possibility that it is normal engine variation.
Logically, it must be either that the loads are significantly different (as could be the case if a prop was damaged, etc.) or that your measurements are wrong. If you are confident in the measurements, I would focus on load, and disregard the possibility that it is normal engine variation.
Although that is possible I would guess that he is asking about a trip that was made at twice that speed or more where prop variations make larger contributions to unequal loading.
But heck - I don't know so lets see what is posted back on this in good time.
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Some reasons:
1. Inaccuracies in calculating fuel burn.
I assume that you are basing your numbers on running each engine from separate tanks and measuring how much it takes to fill each. This method is influenced by how full you got each tank each time you filled and can easily be off 5% up on one and down on the other.
2. Port to starboard gear ratio differences.
This is often the case when the gear box is used to counter rotate port vs starboard.
3. Prop pitch differences.
4. A combination of 2 and 3.
You could adjust the pitch on one or the other prop to get the fuel burn closer.
5. Your genset if running at half load will burn about 1 gph, so not significant in 4 hours.
6. Engine differences
Every engine data sheet says that their numbers could be as much as 3% different which goes both ways. So maybe 3% up on one and 3% down on the other.
The injection pump, injectors, turbo, etc. discussed above are mostly BS.
You don't say what the percentage difference is. Anything less than 10% I wouldn't worry about.
David
1. Inaccuracies in calculating fuel burn.
I assume that you are basing your numbers on running each engine from separate tanks and measuring how much it takes to fill each. This method is influenced by how full you got each tank each time you filled and can easily be off 5% up on one and down on the other.
2. Port to starboard gear ratio differences.
This is often the case when the gear box is used to counter rotate port vs starboard.
3. Prop pitch differences.
4. A combination of 2 and 3.
You could adjust the pitch on one or the other prop to get the fuel burn closer.
5. Your genset if running at half load will burn about 1 gph, so not significant in 4 hours.
6. Engine differences
Every engine data sheet says that their numbers could be as much as 3% different which goes both ways. So maybe 3% up on one and 3% down on the other.
The injection pump, injectors, turbo, etc. discussed above are mostly BS.
You don't say what the percentage difference is. Anything less than 10% I wouldn't worry about.
David
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How are your engines synchronized?
Do your transmissions have the same reduction gearing?
Are your props pitched exactly the same?
Do you run your engines at the same temperature?
All of the above will influence fuel burn. None are easy to compensate for, if those differences exist.
Do your transmissions have the same reduction gearing?
Are your props pitched exactly the same?
Do you run your engines at the same temperature?
All of the above will influence fuel burn. None are easy to compensate for, if those differences exist.
Once again we need sammy999 to post back but I am a bit familiar with his boat so I will put up a few more 'guesstimates".
1. "I assume that you are basing your numbers on running each engine from separate tanks and measuring how much it takes to fill each."
Each tank is amidship and at 222 total gallons each. They tend to fill and refill with no issues as long as you take some care.
"2. Port to starboard gear ratio differences"
Gears are 800 series with both "A" an "B" at 1.96:1
"5. Your genset if running at half load will burn about 1 gph, so not significant in 4 hours."
Estimates from about 0.7 or so are often near the mark on these boats.
"You don't say what the percentage difference is. Anything less than 10% I wouldn't worry about."
With his 490 Pilothouse running at 16 knots over 200 nautical miles Sammy's total fuel burn should be around 222 for a port and stb variation of 98 vs 124.
At hull speeds I will guess that his genset hours would be higher but just making guess's rarely yields good data.
1. "I assume that you are basing your numbers on running each engine from separate tanks and measuring how much it takes to fill each."
Each tank is amidship and at 222 total gallons each. They tend to fill and refill with no issues as long as you take some care.
"2. Port to starboard gear ratio differences"
Gears are 800 series with both "A" an "B" at 1.96:1
"5. Your genset if running at half load will burn about 1 gph, so not significant in 4 hours."
Estimates from about 0.7 or so are often near the mark on these boats.
"You don't say what the percentage difference is. Anything less than 10% I wouldn't worry about."
With his 490 Pilothouse running at 16 knots over 200 nautical miles Sammy's total fuel burn should be around 222 for a port and stb variation of 98 vs 124.
At hull speeds I will guess that his genset hours would be higher but just making guess's rarely yields good data.
Where does the return fuel go? Perhaps all to one tank? How did he measure the fuel usage? I'm sure he'll respond later.
Lepke
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Usually in twin installations with engines of similar condition, fuel consumption differences are caused by loading differences. Engines not in sync. Also if one engine has bilge pump, alternator the other doesn't have.
Get a portable heat gun and check temps of exhaust ports to see if engines are producing similar exhaust gas temperatures. If turbo driven, check boost pressures.
One prop could have slightly more pitch.
Etc...
Get a portable heat gun and check temps of exhaust ports to see if engines are producing similar exhaust gas temperatures. If turbo driven, check boost pressures.
One prop could have slightly more pitch.
Etc...
Capt.Bill11
Guru
Way to little information to even start guessing.
Regarding post #4. When fuel valves are set to return both to one tank the results is moving more than 10 gallons per hour from one tank to the other dependent upon speed at the time. With the same boat we have actually added 100 gal on one side only and used the returns to transfer fuel over the next 4-5 hours to come close to 'equal up'.
Here is a pic of the fuel valves that should be on Sammy's boat....
Here is a pic of the fuel valves that should be on Sammy's boat....
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The Other Gary
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I have the same manifold in my boat. Pretty hard to get it wrong.
FOG
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Another questions to ask the OP, is if this is the one and only time he has seen this difference. Has he previously measured them when the fuel burn was much closer together for the two engines. And if so, what was the difference?
First of all, thanks to all who responded. We bought this boat 16 months ago in Ft Myers, FL and ran it up to Pickwick Lake in MS; about 800 miles. We didn't go far in that time at Pickwick but now we are headed to the Florida Keys and I'm trying to get some good fuel consumption rates going different speeds. Per the above posts, I will try and clarify some things.
1. I calculated the usage based on the number of gals each tank took at fill-up. I tried to fill them the same but understand that this can lead to some discrepancy. We traveled 228 miles over 2 days and took on a total of 212 gals; SB 119 gals and port 93 gals. The 1st day we ran fast at 12.5 mph at 2300 rpm and the 2nd day a lot slower at 9.5 mph at about 1600 rpm.
2. The gear ratio per the survey is 1.96 - 1 for both engines
3. To the best of my knowledge, the running gear is fine and the props are pitched the same.
4. According to the temp gages, the SB runs a little hotter, maybe at 190 vs 185 for the port.
5. I do not have a fuel management system panel. Just levers in the fuel lines for on/off.
6. By making sure the engines are loaded the same, I'm guessing this means ensuring each engine is running at the same RPM.
7. This is where it may get interesting. The tachs were pretty erratic at times. One day one of the bridge tachs was off so I referred to the lower helm tachs, then the next day, the opposite, then the next day either one or the other port or SB tach would be off. I tried to match the RPMs using whichever tach wasn't acting up. Then the next hour they would settle down and seem to be reading accurately.
8. I'm sorry to say I do not know which tank or tanks my return fuel lines go to. The genny does run off the SB but not sure about the return line.
9. The percentage difference between the two tanks seems to be about 23%.
10. This probably doesn't have anything to do with this, but we had a delivery Capt from Ft Myers to Pensacola who ran the genny the whole way (about 40 hrs). The fuel usage at this point was fairly equal. From Pensacola to Pickwick we did not run the genny at all and this was when the fuel usage seems to begin to diverge.
You all have given me some things to check out, especially the tachs, engine temp, and fuel line returns. Thanks again and any more input is much appreciated!!
1. I calculated the usage based on the number of gals each tank took at fill-up. I tried to fill them the same but understand that this can lead to some discrepancy. We traveled 228 miles over 2 days and took on a total of 212 gals; SB 119 gals and port 93 gals. The 1st day we ran fast at 12.5 mph at 2300 rpm and the 2nd day a lot slower at 9.5 mph at about 1600 rpm.
2. The gear ratio per the survey is 1.96 - 1 for both engines
3. To the best of my knowledge, the running gear is fine and the props are pitched the same.
4. According to the temp gages, the SB runs a little hotter, maybe at 190 vs 185 for the port.
5. I do not have a fuel management system panel. Just levers in the fuel lines for on/off.
6. By making sure the engines are loaded the same, I'm guessing this means ensuring each engine is running at the same RPM.
7. This is where it may get interesting. The tachs were pretty erratic at times. One day one of the bridge tachs was off so I referred to the lower helm tachs, then the next day, the opposite, then the next day either one or the other port or SB tach would be off. I tried to match the RPMs using whichever tach wasn't acting up. Then the next hour they would settle down and seem to be reading accurately.
8. I'm sorry to say I do not know which tank or tanks my return fuel lines go to. The genny does run off the SB but not sure about the return line.
9. The percentage difference between the two tanks seems to be about 23%.
10. This probably doesn't have anything to do with this, but we had a delivery Capt from Ft Myers to Pensacola who ran the genny the whole way (about 40 hrs). The fuel usage at this point was fairly equal. From Pensacola to Pickwick we did not run the genny at all and this was when the fuel usage seems to begin to diverge.
You all have given me some things to check out, especially the tachs, engine temp, and fuel line returns. Thanks again and any more input is much appreciated!!
Hello Sammy999, a few observations on your posts...
- I suggest getting a strobe tach and verifying and correcting your boats tachs before continued cruising
- If you have done that already then can you reach rated WOT + 3-5% as a brief test in gear?
- Your fuel tanks are fairly easy to fill with repeatability. That is mostly because they are almost rectangular from the bottom up (save for the first 6 inches on the bottom) and have fill hoses that drop almost straight down from the fill cap to the tank. Each tank is right about 24" tall with each inch 'holding" about 9 gallons. So your 26 gallons would represent 3" of tank level.
- Generally running at 12.5 mph is close to about the worst speed you can run at for efficiency. Either run lower than 8 knots or higher than 14 knots for added efficiencies. I also would suggest adding EGT and boost gages as the y are not very expensive and will prevent you from inadvertently lowering your engine life. Running at 2300 you are likely into the turbo's and I have seen some higher than wanted EGT's in that range.
- You will need to figure out your fuel valves and selection to answer some of your own questions. That boat came with a full fuel valve manifold so someone modified it at some point in time. If you ran the genset for 40 hours and it pulled and returned to the same tank then that tank would have used about 28 gallons of fuel. Dependent upon the loads on the genset at the time it could be as low as 12 or as high as 50 gallons.
- This question - "I'm trying to get some good fuel consumption rates going different speeds."
Here are some general guidelines that have been rounded to whole numbers so they are easy to remember but still will be very close (yes made to seem simpler for my own simple memory)....
6 knots - near 4 nmpg
8 knots - about 2 nmpg
10 knots - about 1 nmpg
16 knots - about 0.9 nmpg
You will find at least 20 4788 owners who post frequently over at the Bayliner ownersclub where yo just posted earlier.
Hope this helps
- I suggest getting a strobe tach and verifying and correcting your boats tachs before continued cruising
- If you have done that already then can you reach rated WOT + 3-5% as a brief test in gear?
- Your fuel tanks are fairly easy to fill with repeatability. That is mostly because they are almost rectangular from the bottom up (save for the first 6 inches on the bottom) and have fill hoses that drop almost straight down from the fill cap to the tank. Each tank is right about 24" tall with each inch 'holding" about 9 gallons. So your 26 gallons would represent 3" of tank level.
- Generally running at 12.5 mph is close to about the worst speed you can run at for efficiency. Either run lower than 8 knots or higher than 14 knots for added efficiencies. I also would suggest adding EGT and boost gages as the y are not very expensive and will prevent you from inadvertently lowering your engine life. Running at 2300 you are likely into the turbo's and I have seen some higher than wanted EGT's in that range.
- You will need to figure out your fuel valves and selection to answer some of your own questions. That boat came with a full fuel valve manifold so someone modified it at some point in time. If you ran the genset for 40 hours and it pulled and returned to the same tank then that tank would have used about 28 gallons of fuel. Dependent upon the loads on the genset at the time it could be as low as 12 or as high as 50 gallons.
- This question - "I'm trying to get some good fuel consumption rates going different speeds."
Here are some general guidelines that have been rounded to whole numbers so they are easy to remember but still will be very close (yes made to seem simpler for my own simple memory)....
6 knots - near 4 nmpg
8 knots - about 2 nmpg
10 knots - about 1 nmpg
16 knots - about 0.9 nmpg
You will find at least 20 4788 owners who post frequently over at the Bayliner ownersclub where yo just posted earlier.
Hope this helps
You have two clues.
Erratic tachs
SB running a bit hotter.
Load can not be measured by RPM. Consider that an engine can run at any RPM out of gear and have no load. At a fixed RPM an engine can produce from zero HP to max rated all at the same RPM.
Load=fuel use, always. My suspicion is that the SB engine is using more fuel because it is doing more work. yes there could be something wrong with it or the prop or the data could be wrong but the temp is a clue, if correct.
The simplest answer is usually correct, more load.
Do both engines reah the same WOT RPM or is the SB a little less?
As above do get a photo tachometer and calibrate your tachs. If the tach reads low you would add fuel to increase its output, and RPM, and thus more fuel.
Erratic tachs
SB running a bit hotter.
Load can not be measured by RPM. Consider that an engine can run at any RPM out of gear and have no load. At a fixed RPM an engine can produce from zero HP to max rated all at the same RPM.
Load=fuel use, always. My suspicion is that the SB engine is using more fuel because it is doing more work. yes there could be something wrong with it or the prop or the data could be wrong but the temp is a clue, if correct.
The simplest answer is usually correct, more load.
Do both engines reah the same WOT RPM or is the SB a little less?
As above do get a photo tachometer and calibrate your tachs. If the tach reads low you would add fuel to increase its output, and RPM, and thus more fuel.
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Panacea123
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Fuel usage
Interesting situation!
Have had similar results but finally figured it out (for me anyway)
First off, do you have equalizing fuel lines on your tanks?
Mine does, with shut off valves, so gravity will equalize the tanks regardless of fuel burn.
When refueling my stbd tank, by the time if was full aprox 20 gal would have moved over to the port tank via the connecting line at the bottom of the tank, thus giving the illusion the stb tank took on more fuel!
Hope this helps
Interesting situation!
Have had similar results but finally figured it out (for me anyway)
First off, do you have equalizing fuel lines on your tanks?
Mine does, with shut off valves, so gravity will equalize the tanks regardless of fuel burn.
When refueling my stbd tank, by the time if was full aprox 20 gal would have moved over to the port tank via the connecting line at the bottom of the tank, thus giving the illusion the stb tank took on more fuel!
Hope this helps
A few more thoughts for Sammy....
- If you do not a handbook they are quite helpful and available online.
- These boats came from the factory with too ,much prop pitch. Does your survey tell you what you have for props? (24 X 24 is too much)
- You will need EGT gages to determine if you are running hot or not. The stock temp gages are close at best and even when accurate do not show relative load on these engines. Often just by cleaning the electrical connection on the gage or the sender the gages will become less finicky and slightly more accurate.
- If you do not a handbook they are quite helpful and available online.
- These boats came from the factory with too ,much prop pitch. Does your survey tell you what you have for props? (24 X 24 is too much)
- You will need EGT gages to determine if you are running hot or not. The stock temp gages are close at best and even when accurate do not show relative load on these engines. Often just by cleaning the electrical connection on the gage or the sender the gages will become less finicky and slightly more accurate.
