Fuel consumption based on flowscan

[Peter.D]

I own a 1997 272 sailfish with T225 yamahas.
My last trip I wrote down the total gallons used and compared them when I returned from a rather short and lightly loaded trip. I burned 43 gallons going 38 miles at 26knts based on gps.
I understand about bottom growth and speed loss, tide, waves , wind etc.
The bottom was power washed 1 month ago.
What do you think of these numbers?
Thats less then 1nm per gallon. Does anyone else have a simular set up.
Thanks.

 

[choogenboom]

My twin 2004 F225's run at about 1-1.2 mile/gallon or about 35-38 GPH at WOT. So your numbers for older 225 two strokes do not sound too far out of line.

1 month of growth in RI could also be meaningful.

 

[gw204]

What was the water like during that run? Confused? Clam?

My '93 252G used to get about 1.6 mpg cruising on flat water.

 

[Peter.D]

Thanks for the replies

The water was 2' waves in Narragansett bay with 15knot wind on our back. We did have to face the wind on the way back but thank god for enclosures. This was the first time I noted fuel consumption, so I will have to keep an eye out.
Thanks

 

[Tunacious D]

Our 93 Sailfish with carbed 200 yamahas would have delivered about that same number on a windy day, at that speed, and with enclosure up (lots of resistance).

A couple of things to consider: How confident are you that your floscan is/was calibrated? Does it interface with the GPS to give you calculated nmpg? The 38 miles from your GPS is it miles or nautical miles?

 

[downtown]

Will the floscan give you gallons burned at the end of the day?

 

[Tunacious D]

The model 9000 I have gives you instanteous gph by engine, total gallons for the trip or total burned since last reset, and mpg or nmpg depending on how you have the GPS setup. I decided to stay with the FLOSCAN even though the new motors came with Yamaha's FMS. As long as you spend some time with the calibration, it is quite accurate. When installed the first time, it was around 4% off (high). Dialed it in over the next three trips and now it is less than 1%. Really gives you piece of mind knowing how much is in the tanks and how to trim the boat for the best burn.

 

[Peter.D]

Thanks for info

Seems I have to use the boat more to get averages. I had gone to the block, mud hole and back on 70 gallons in moderate seas. I think I am averaging 1.5 nautical miles which is less than I like but the comfort and quality I am bringing its worth it. Hey, Gas is down now too!! Too bad she is on blocks.\
Peter

 

[striped bass]

I have to have the bottom cleaned about every two weeks on my GW Tournament. It is moored all season in Watch Hill harbor and the bottom growth can be substantial. Since you are in RI, I expect that one month of growth on your boat bottom had an effect on your gas consumption. I also have a Herreshoff sail boat which is cleaned every week since I know the bottom growth impeeds speed and performance when it is raced each Saturday. Try taking a reading next season right after you have cleaned he bottom.

 

[seasick]

The gas mileage you read about for a specific vessel/motor combination are usually at one specific RPM value. Consumption can double or more at WOT versus that sweet spot.
If you cruise at WOT or close to it, your consumption will be much higher than optimal.
For my motor, the sweet spot is about 3800 RPM.

Refer to the Grady web site, pick a boat/motor combo close to yours and open up the specifications. Take a look at the fuel consumption tables.

Note that the fuel consumption rate doesn't tell the whole story if you are running to a particular fishing spot. If your consumption rate is 30% higher than the sweet spot but you get there in 30% less time, the total fuel consumption is about the same.
On the other hand, if you are cruising for 4 hours, cruising at WOT will burn a lot more fuel than cruising at optimal RPMs.

 

[BobP]

Downtown, mark the gauge figure at start of the day, then by end of the day you will know how much fuel was used.

 

[downtown]

Thanks, Bob.

 

[Peter.D]

Thanks for input

Thank you for you advice.
I have been noting my start gallons with my finish gallons consumed. I never realized how big the boat was until it was placed in my yard!! These engines are pushing a hell of a lot and with the hard top and full enclosure ther is 9.5 feet in the air!!! One note.. The bottom was pretty clean with slight growth. I think I need practice with the trim tabs. By the way, how many bars do people use on the engine trim? I think i was on 3 bars .