Gas consumption

[Shaun Quilty]

I have a 2006 38' Sundancer which I just bought. They are big blocks 8.0 HO. Both engines were just tuned up. I brought the boat back from Portland Maine to Boston. My starboard engine used 22 more gallons on a 5-1/2 hour trip. Any ideas?

 

[carterchapman]

Was the genny running? On my 340, the generator feeds from the stbd tank.

 

[dc380]

Are you sure both tanks were filled to the same level?

I know it's hard for me to get them prefectly full without letting them spit out the overflow... And even then one spits sooner then the other.

Were both engines in sync during the ride back? Making one do more work can burn a lot of fuel.

 

[Aerobaticflyer]

Are you basing your uneven fuel consumption on your "Smartcraft" readings? I have found mine to be way off. Last week I ran 35+ nautical miles on 0% fuel in my starboard tank! I did this because I filled the tanks myself and both tanks always take the same amount of fuel and I know I ran both engines in sync. Something wrong in the calibration or something.

FWIW the generator consumes very little fuel relatively speaking so I have found it to be almost a non-issue unless being on the hook for a long time with a lot of generator run time. Just running it while underway has very little effect in overall fuel consumption in my experience.

 

[Shaun Quilty]

Both were in sync. I did not run the gen on the ride back. I also notice the starboard gas gauge drops quicker than the port

 

[dc380]

What does the Starboard engine oil look like?
Was the gas in the boat relatively fresh?

 

[Shaun Quilty]

Oil is very clean. The gas was fresh but who really knows

 

[earthmover17]

How did you determine you used 22 more gallons? Did you fill the tanks when you got in? Also as previous poster said who filled the tanks from the get go. I would fill em up personally and take it out and check that way before I got to concerned.
Jack

 

[Hampton]

My guess is that your props have been to the shop and they were matched. They should not be matched. The port prop should have about .5" more pitch. This is because one transmission runs in forward and one runs in reverse. They are geared differently. They come from the factory mis-matched.

I had the exact same symptoms. I took my props to a very reputable prop shop with a computerized scanner. They confirmed the issue. It took two trips, but now the engines burn the exact same fuel. Search my name and this topic and you will find a post from about Jan 2008 that gives all of the final results.

 

[Shaun Quilty]

I filled them when I got back. They were originally filled by the dealer. I know that you can't trust the gauges but the starboard gauge is a 1/4 less than the port.

Thanks Jack

 

[Hampton]

http://clubsearay.com/forum/showthread.php?t=6461&page=4&highlight=props

 

[Shaun Quilty]

Thanks John. That was my thought also

 

[BahamasBlair]

If you are reading from the Smartcraft gauges - forget it ! They are very unreliable. The only way i have found to get a handle on consumption is to fill the tanks on both sides, run for a few hours on a trip and then fill up again. Check your miles run with your GPS and make the calcs.
Another issue is the spark plugs. If they haven't been changed in a long while you will get crappy mileage. I'm changing mine this weekend.

 

[sdowdy]

I had the same problem on my 38. I turns out that one of the spark plug wires was not making a full connection. I had both engines in sync and the only thing I noticed was higher fuel consumption. The engine works harder to compensate for the bad cylinder firing and thus uses more gas.

Check your plug wires.