Higher Fuel Consumption on Port Engine

Would it be possible to switch the flow computers?
 
I don't believe there is any kind of flow computer or sensor. It's just data on the SmartCraft Bus from the ECM. I think the most accurate thing for me to do is to fill up and run without the generator and fill up again.

I could verify the RPM readings on my engines but isn't Smartcraft RPM always accurate?
 
Every inboard boat I owned, one motor burned more fuel than the other (34c gas, measured by B&G, 290 AmberJack, measured by Smart Craft, 45c diesel, measured by that volvo thing :).
 
How often do you run the generator compared to running the port engine? Do you use it underway? Could you be running it more now than when you recall fuel burn was more even between engines? Obviously fuel burn should be higher on the port side if both mains and the genny are all running.

You mentioned "gas engines" in response to the crossover valve question. I'd guess probably the majority of twin gassers with 2 tanks have a crossover valve setup but keep the valve closed except for emergencies or rarely ,balancing functions.
 
Does your Smartcraft system have any calibration function for GPH and G/U Totalizer?

On my 27'w/ tw/ I/B gas MPI's( non-return) I have 2 FloScan 9000's that use inline flow-meters ...and.. a B&G NetEngSys display (redundant systems that use different kind of sources). Along with other ECM data, the latter reads ECM (algorithm-derived-data-from-injector-pulse-frequency-and-time) GPH and resettable G/U Totalizer same as your Smartcraft, .... point being: both the FloScan and B&G are user-calibratable for accuracy.

The B&G actually proves a bit more accurate of the 2 during most all fill-ups . There is still usually a bit of differential in displayed NGPH between running engines and between the redundant displays (and more at low rpm) but at the pump the actual pumped topped up fill of each independent 100gal tank is generally within .2 to 2.0 gal of the other .

As you mentioned, the only way to really know for sure if your mains really are or aren't burning essentially identical GPH is to top both tanks and keep the genny off and re-top-off after a substantial trip. More than once would be better.
 
I run the generator almost always when underway. I'm basing fuel burn on SmartCraft, not just the fact that I am putting more gas in the port tank. I don't think that crossovers are used with gas but I forget the reason. It would be nice if the two tanks were connected like my water tanks but they definitely are not on my boat.

I don't believe there is any adjustment or calibration on the Smartcraft for fuel burn.
 
If the fuel pressure is different on the two engines the computer will compensate by changing the injector duration to deliver equal amounts of fuel and maintain correct mixture but the smartcraft assumes a fixed amount of fuel per injector dwell so it will report out a different fuel burn. It could also be a sluggish O2 sensor misreporting a lean condition and the computer is adapting with more fuel. You really are shooting in the dark without hooking up a scanner and having someone that knows how to read the data.
 
NB. Michaelis reporting that his fuel use was equal now its not, something changed.
 
Smitty he said that the port was over propped, port usually uses more fuel with a reversing tranny. That's why I asked if the over / under propping data could be reversed. He said the fuel use increased before he tuned the props and didn't change with the tuning. Strange.
 
I hear you Bruce - I am just betting it is load related. You don't use that much difference in fuel without some plug issues or fuel sheen or carbon black on the outlets related to engine issues unless it is load related.
Michael has the prop specs before and after , he has the history he has kept in the logs, and he has the transmission tags on his boat. It is fairly easy to guess the fuel use of a genset by size and load to adjust for that variable. At this point the engines truly seem to be in good shape so I am hoping this lets him piece together the other parts of this equation.
These types of issues come up quite frequently on BOC and this Meridian I a very close relative to those boats. When a post reads like this nine times out of ten the answer ends up being load related (props / trans ratio / hits to prop / etc) after very long strings of possibilities.

Hope this helps
 
I agree usually load related BUT this is a change from previous equal use. The prop report is the opposite of what I would expect but the problem predates that and there is no report of any dinged prop.
 
Genny fuel usage will not show up on the Smartcraft. It's not a flowscan with an inline sensor it just reads injector data. The only reason the genny was mentioned was in relation to the fill up data potentially being misleading. A controlled 5% rich caused by an O2 sensor will not result in carbon or fuel sheen since it is being burned just not optimum.
 
Good information. I will check the transmissions. I Guess I could swap O2 sensors as a test. That would be interesting. Didn't know there were O2 sensors in the absence of catalytic converters.

Generator only burns about 1/4 gal per hour. Even if it ran 20 hours between fill ups and even if it used 1/2 gallon, that would only be a 10 gallons of gas.
 
I just looked at the Part Manual. They list the transmission as a Velvet Drive 5000 2.8 No differentiation between port and starboard. My understanding is that both transmissions rotate the same way but that one is configured to run in reverse and one in forward when the shifters are both placed in forward. The specs on both props are also the same. This leads me to believe that ratios are the same. Is it true that reverse uses an additional gear to get the opposite rotation? If so, does this really put additional load on the engine?
 
Just called the Velvet Drive Factory. The transmission is fully reversible. There is no additional gear when placed in the reverse configuration and there should be no additional load on the port side transmission. Props are pitched the same.
 
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