fuel consumption 290 amberjack, twin mag350's, v-drive

J

jchoe98

New Member
Feb 26, 2011
13
san diego
Boat Info
amberjack 290, 2007
Engines
twin 350HP Mercruiser MPI Horizon's, v-drive
hello all. i love my boat but i feel like i burn a heck of a lot of fuel and wanted to get your advice/thoughts.
to be more specific, here's my boat condition and how she ran this past weekend:
- bottom powerwashed (1 week ago)
- 2 adults
- full tank of gas
- twin mag350's, v-drive
- compression test completed last year, perfect
- i ran her for 30 miles at 3700 rpms (planes best at 3700, goes about 26 knots)
-i burned 30 gallons in each tank (ie - 60 gallons total)

question #1) does this sound about right? if so, this puts me in the max range of about 110 miles when going 3700 rpms at 26 knots.

how do i know i burned 30 gallons in each tank? because i filled the gas to the top before and refilled back up to the top after.

question #2) i have port and starboard tanks and they seem to be totally separate from each other. ie - if one tank ran dry, then i would only run on one engine until i can refill the other tank. is this correct?

thanks all in advance for your thoughts/advice/opinions.
 
I have a 2001 290 Amberjack with twin MerCruiser 5.7L 350 EFI, First time out yesterday! :thumbsup: I do not know what my fuel mileage was exactly but it did a lot better than I expected. We stayed out on the boat all weekend and put on approximately 70 miles. I had 3/4 of a tank when I left and I used about 1/3 of a tank, in both tanks. I also ran the generator when we parked and I was told the generator uses 1 gal/hr. Both tanks are independent of each other so if one runs out of gas, you will have to run on the remaining engine only. I had the boat surveyed two weeks ago and they did an analysis of where she ran the best. Below is what they determined. I ran the boat at the recommended 3200 most of the time and it really did seem to handle well and run very smooth. In comparison, if you were running at 3700 rpm at less mph than I am at 3200 rpm, I expect your mph may be incorrect.
 
Ooops! The graph did not post. Here you go.

1000 RPM = 5.9 kts
1400 RPM = 6.8 kts
2200 Rpm = 9.1 kts
3200 RPM = 26.6 kts
3600 RPM = 31.2 kts
3800 RPM = 35.8 kts Speed was In Knots @ RPM
1 Knot - 1 Nautical MPH
1 Nautical MPH = 1.15 (Land) MPH
Knot(s) = MPH
7 Nautical MPH = 8(Land) MPH
 
do you each know what diameter and pitch of props. Both inboards correct? Jchoe .5 miles per gallon sounds real low but you are running 3700 rpm which sounds high. Are you keeping trim tabs in up or down position?
Viking is doing 500 less RPM to achieve same speed. I know they are different year boats, is there a big weight difference? Beams equal.
I have a friend who has 07 I believe. when I see him I will ask him what his consumption and rpm vs knots and let you know
 
Viking said:
Ooops! The graph did not post. Here you go.

1000 RPM = 5.9 kts
1400 RPM = 6.8 kts
2200 Rpm = 9.1 kts
3200 RPM = 26.6 kts
3600 RPM = 31.2 kts
3800 RPM = 35.8 kts Speed was In Knots @ RPM
1 Knot - 1 Nautical MPH
1 Nautical MPH = 1.15 (Land) MPH
Knot(s) = MPH
7 Nautical MPH = 8(Land) MPH
Click to expand...

This is for I/O and not v drive I believe. The boat is considerably slower with v drives.
 
jchoe98 said:
hello all. i love my boat but i feel like i burn a heck of a lot of fuel and wanted to get your advice/thoughts.
to be more specific, here's my boat condition and how she ran this past weekend:
- bottom powerwashed (1 week ago)
- 2 adults
- full tank of gas
- twin mag350's, v-drive
- compression test completed last year, perfect
- i ran her for 30 miles at 3700 rpms (planes best at 3700, goes about 26 knots)
-i burned 30 gallons in each tank (ie - 60 gallons total)

question #1) does this sound about right? if so, this puts me in the max range of about 110 miles when going 3700 rpms at 26 knots.

how do i know i burned 30 gallons in each tank? because i filled the gas to the top before and refilled back up to the top after.

question #2) i have port and starboard tanks and they seem to be totally separate from each other. ie - if one tank ran dry, then i would only run on one engine until i can refill the other tank. is this correct?

thanks all in advance for your thoughts/advice/opinions.
Click to expand...

26 knots at 3700 on a v - drive boat is absolutely phenomenal . Most if not all v drive 290'see about 24 knots at 37-3800. Are you sure about your unit of measure. (i.e., mph vs knots)? Your fuel burn seems way off.

You should be burning about 28-30 an hour or .8 -1 MPG with a 3 blade prop., and about 24-26 an hour on a 4 blade prop. The above is what I see and has been what most other AJ owners see. These boats are pigs with v drives; lots of drag with running gear as opposed to I/o, but if you are in salt , you don't have added maintenance that comes with out drives; but you do indeed give up performance and fuel efficiency in a BIG way. Your fuel tanks are completely separate; there is no sharing or crossover, so yes, if you run one dry, you will be on one engine and the boat will not plane on one drive. 8 knots is max speed on one drive. Lastly, use about 1 mpg as a way to know what your burning. Keep both tanks at same level always. If you have a generator it will burn off starboard side so adjust for that as well when filling up. The fuel burn can be monitored on your smart craft gauges.
 
Last edited:
wakeup 19 said:
do you each know what diameter and pitch of props. Both inboards correct? Jchoe .5 miles per gallon sounds real low but you are running 3700 rpm which sounds high. Are you keeping trim tabs in up or down position?
Viking is doing 500 less RPM to achieve same speed. I know they are different year boats, is there a big weight difference? Beams equal.
I have a friend who has 07 I believe. when I see him I will ask him what his consumption and rpm vs knots and let you know
Click to expand...

Yes, props are 14" diameter X 22" pitch. Yes, inboards. Should be same weight and beam.
 
"Yes, props are 14" diameter X 22" pitch. Yes, inboards. Should be same weight and beam."

That seems way off for pitch and diameter. I think 16x17 cupped are standard props for 2001 350 mag inboards.
 
I know this is an old thread. But I just got my 2005 290 AJ last Sept. today we took her on her 1st long trip. Approx 60 miles from Cleveland to Kelly’s island. We started with just shy of a full tank in between 3/4 in full after going 60 miles on our trip the gauges are reading in both tanks 1/4 of a tank I have to 100 gallon tanks. So if my math is correct we have a proximately 25 gallons in each tank totaling 50 and we started with around 175 I’m assuming so that’s 125 gallon tanks for one 60 mile trip that seems really excessive to me boat ran fine it was a little choppy we averaged around 3300 to 3500 RPMs traveling around 26 to 29 knots
 
Boat fuel gauges are designed to save us from ourselves by being so wildly pessimistic that we’ll never run out of gas. They can’t by relied on to determine fuel consumption per mile.
 
1/2 tank off?

Mine read between 1/4 and 1/3 too low.

I installed fuel meters that allow the Garmins to calculate total fuel onboard. I haven’t looked at the gauges since.
 
RollerCoastr said:
1/2 tank off?

Mine read between 1/4 and 1/3 too low.

I installed fuel meters that allow the Garmins to calculate total fuel onboard. I haven’t looked at the gauges since.
Click to expand...

fuel meters ??? I’m planing on upgrading my electronics to garmin this winter when it’s out of the water ? It still has the original 2005 Lowrance. And even though it does have engine Monitoring. I do not believe it is hooked up ?? How hard is it to install fuel meters ??
 
Viking said:
I have a 2001 290 Amberjack with twin MerCruiser 5.7L 350 EFI, First time out yesterday! :thumbsup: I do not know what my fuel mileage was exactly but it did a lot better than I expected. We stayed out on the boat all weekend and put on approximately 70 miles. I had 3/4 of a tank when I left and I used about 1/3 of a tank, in both tanks. I also ran the generator when we parked and I was told the generator uses 1 gal/hr. Both tanks are independent of each other so if one runs out of gas, you will have to run on the remaining engine only. I had the boat surveyed two weeks ago and they did an analysis of where she ran the best. Below is what they determined. I ran the boat at the recommended 3200 most of the time and it really did seem to handle well and run very smooth. In comparison, if you were running at 3700 rpm at less mph than I am at 3200 rpm, I expect your mph may be incorrect.
Click to expand...
 
Seems yours may be doing a little better than mine. We took a trip approx 55 miles one way. We left I had just under 3/4 in both tanks or at least that is what it read. When we got to destination I had just under 1/4, at least what it was reading. So according to that we used 1/2 tank in both tanks to go 55 miles. That would be approx 57 gals in each tank or 114 total. To go 55 miles !!! Seems really high

Now heading there we were going against the wind/current with a little chop. So I had to keep the rpm’s down 2800-3000. Going 24-28 mph.

and again we filled up at the gas station before heading back 55 miles and tanks were reading just under 1/4 and it only took approx 60 gal in each tank to fill full. My tanks are 115 gal each ??

I’ve factory reset the smartcraft guages , and calibrated them to 115gal. But something is off. I’m not using as much fuel as they are reading. That’s good I guess

I went out the other day when it was nice and smooth on the lake and I used your chart to check my speeds with rpm’s. And they seem to be right on the money what the chart says.

do you know if there is a fuel guage sender In the tanks maybe it is bad. I looked for it and could not see where it may be or how to replace it. Or is gauges all electronically controlled etc

appreciate your thoughts. Thx
 
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