Fuel burn rate and volume on a jet boat?

Lem Lamb

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368 liters/ 80 imperial gallons = 1 1/2 hours at full throttle...

Spent funds ='s good times !!!
 

ctd

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I'm the wrong guy to ask these questions too... all my shits got Berkeleys, carburetors and distributors... but I have spent enough time in LSA powered boats to never surprised by how much fuel they can drink. We were just doing a 62 mile pre run the other day, so 125 miles total... the 21 sport would drink a full fuel tank (200+ liters?) plus 4 jerry cans (80 liters) to get back... but we were over 50 mph and 4000rpm the whole time.

so a boosted, port injected 6.2L motor will burn a lot more than a DI, NA, 6.2L motor... look at the power difference... the LSA will pull the same impeller 1000 rpm higher, that's torque and it takes fuel.

100% I agree.

The chart is comparing boosted to a DI? If so I agree, substantial power difference so the chart is meaningless.......power = fuel.
 

ctd

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The DI runs higher compression among other things, higher compression ratios are more efficient, being the primary driver why diesel engines are more efficient than gas. The DI has a higher efficiency across its entire operating range than the LSA due to this. I believe the LSA is running 9:1 where the DI is 11:1.

Also add in the parasitic loss of a supercharger, it takes a lot of HP from the crank to shove even a few psi of boost into the intake of a big V8. Yes it adds more power, but efficiency drops drastically at that point.

Keep in mind a good gasoline engine only converts 30-35% of the energy in the fuel into mechanical work, the rest is lost as heat. Going from say 30% to 35% efficiency makes about a 15% difference in fuel consumption.

I did not realize the chart was comparing a SC motor to a NA, makes the thing useless rationalizing GPH. If you were to compare DI NA to a LS NA, same engine size & power output you would see a very small difference in GPH.

Diesel is a different game entirely.
 

ABMax24

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I did not realize the chart was comparing a SC motor to a NA, makes the thing useless rationalizing GPH. If you were to compare DI NA to a LS NA, same engine size & power output you would see a very small difference in GPH.

Diesel is a different game entirely.

It's perfectly rational and useful, 2 identical boats with these engines travelling at the same speed, the DI burns less fuel. Until the LSA punches it and leaves the DI behind.
 

MK4TDI

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I emailed Floscan, hopefully that works for me.

Yes I have a gauge, however its not real accurate. The trouble is when a jetboat looses power say from running out of gas it becomes unhandleable, no rudder on a jet. So your at the mercy of the situation, if your in a corner you'll end up sending it straight off the corner into the bush, possibly hurting someone or at least damaging your boat. If your near log jams it could sink your boat, rocks, rapids non of them will work out good if you loose all control of your boat.

I went to tuchodi lake a few years ago and said I'd never go back without a meter of some kind and I am trying to plan a trip back, hence the attempt again for a meter. Tuchodi lake is 100miles one way, you need to haul gas and manage your gas carefully. On the way in your super heavy with camp and extra fuel so you burn more than expected, then you arrive at the lake and you want to tour around and fish, but you need to keep enough gas to get the 100miles back to the truck. Would be nice on day 10 to know you have burned 400 liters of your 600 liter supply.

If that makes sense.

I done the best I could with my gauge and dipping the tank etc. last time. I ended up coming home with 143L in my tank, would have done more at the lake had I known how much I had used to date.
Do those engines have an OBD port ? Could you run something like the Banks iDash for data monitoring .

 

ctd

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It's perfectly rational and useful, 2 identical boats with these engines travelling at the same speed, the DI burns less fuel. Until the LSA punches it and leaves the DI behind.

The DI will burn slightly less fuel, not dramatically. Comparing NA to NA, when you go WOT it takes fuel regardless how you do it. SC the DI engine & you are back to burning fuel, similar to the SC LS motor.
 

snoflake

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I'm the wrong guy to ask these questions too... all my shits got Berkeleys, carburetors and distributors... but I have spent enough time in LSA powered boats to never surprised by how much fuel they can drink. We were just doing a 62 mile pre run the other day, so 125 miles total... the 21 sport would drink a full fuel tank (200+ liters?) plus 4 jerry cans (80 liters) to get back... but we were over 50 mph and 4000rpm the whole time.

so a boosted, port injected 6.2L motor will burn a lot more than a DI, NA, 6.2L motor... look at the power difference... the LSA will pull the same impeller 1000 rpm higher, that's torque and it takes fuel.
You forgot to mention the person driving the pre run boat does not require a traditional gas pedal. If its started and running, assume its WOT. :LOL:
 

snoflake

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they just dont seem to be accurate due to the angle or something... some of the Firefish have the plastic fuel tanks visible on the sides of the boat, slick system!
Ya, having clear saddle tanks makes calculating very easy. Especially if your pulling out of one tank at a time. Just need to mark how many liters it take's to get to 1/4 tank, 1/2 tank 3/4 and full. Mark your hr's then check when your down a quarter tank. Do this both for upstream and down stream and bobs your uncle. Of course rpm plays a factor, so do it your average cruise speed. I don't trust any in-tank fuel gauges as they all seem to be erroneous at some point in time. Usually when you need them the most.
 

snoflake

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I emailed Floscan, hopefully that works for me.

Yes I have a gauge, however its not real accurate. The trouble is when a jetboat looses power say from running out of gas it becomes unhandleable, no rudder on a jet. So your at the mercy of the situation, if your in a corner you'll end up sending it straight off the corner into the bush, possibly hurting someone or at least damaging your boat. If your near log jams it could sink your boat, rocks, rapids non of them will work out good if you loose all control of your boat.

I went to tuchodi lake a few years ago and said I'd never go back without a meter of some kind and I am trying to plan a trip back, hence the attempt again for a meter. Tuchodi lake is 100miles one way, you need to haul gas and manage your gas carefully. On the way in your super heavy with camp and extra fuel so you burn more than expected, then you arrive at the lake and you want to tour around and fish, but you need to keep enough gas to get the 100miles back to the truck. Would be nice on day 10 to know you have burned 400 liters of your 600 liter supply.

If that makes sense.

I done the best I could with my gauge and dipping the tank etc. last time. I ended up coming home with 143L in my tank, would have done more at the lake had I known how much I had used to date.
I was schooled on the Tuchodi to Leave fuel at the mouth of the Tuchodi and Muskwa, and at the top. We only saved 5 gallons at the lake to get down to the the Muskwa (made sure the boat had a 1/4 tank), and we left 10 Gallons at the mouth of the Muskwa and Tuchodi. This was running 6.2 and Hamilton set up. Had over a quarter tank when we got to the boat launch. The river was boiling on the way down and pouring rain so we were going pretty slow. however, one needs to consider breaking down and towing. Funny that the mini boats burnt way more fuel than bigger boats with V8s.
 
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