8.1 Uneven Fuel Burn

[lawbee]

I've searched (and read) the many past threads regarding fuel burn rates for the Horizon 8.1's. Just returned from seeing how my boat did earlier today. Test conditions: Wind NE 10-12, Sea slight chop, two persons, full fuel, 1/2 H20, clean hull. My results show significantly less than acceptable MPG:
RPM MPH GPH MPG
3000 14.5 27.7 .52
3400 19.8 35.2 .56
3500 20.6 37.0 .55
3800 23.0 47.6 .48
4000 25.9 52.7 .49

WOT was also unusual: Port Engine 4150 RPM; Starboard 4000 RPM at 26 MPH.

Also, burn rate for fuel for 30 min. ride at 16 mph average the port tank burned 3.7 gallons; starboard burned 10.59 gallons-Really!!!!. ALL numbers come from SmartCraft. Any suggestions on what might help MPG numbers (besides diesels-I know I Know-this thing is thursty)? Also, what might be the cause of the wildly differnt burn rates for the engines and what might cure it? Lastly, WOT is different for port and starboard and seems low as I understand from historical threads that WOT should be 4200-4600 at max 38 mph. Is WOT data, uneven burn rate, and MPG data that unusual. I truly appreciate any suggestions. I have mechanic lined up for later this week. You folks are great, thanks!!

_______________________
2004 390 DA, Twin 8.1 Horizons
NE Florida

 

[promocop]

Same issues...minus the uneven fuel burn. I posted to find someone who had the same boat as ours with Diesels to see what their burn rate is...no takers!

 

[bluebelly]

Something is way off. I would inspect the following in this order; props, bottom, fuel filters(both in line and fuel seperating), air flow to the engines(is the performance the same with the engine hatch up?), clean spark arrestors, transmission fluid. Check the alarm history in the smart craft unit. How old is your fuel. Old fuel may be full of water and you have (suffocated) your fuel separators with water.

Good luck

 

[lawbee]

Thanks Bluebelly. FYI the fuel was old (2 months). I had been trying to run it out before re-fueling yesterday. Also, I know the filters have not been changed in well over a year and I'm not putting many hours on the boat between fuelings. I'll check these items this week and post results.

___________________
2004 390 DA, Twin 8.1 Horizons
NE Florida

 

[Octopus IV]

any updates????