Fuel burn rate and volume on a jet boat?

[174mcx]

I was looking a few years ago for a fuel burn rate and volume reading on my Firefish with a 6.2 Kodiak. Does anyone know of anything?

Garmin makes a sensor (gts10) you hook into your fishfinder which does exactly what I’m after, but doesn’t work with a fuel return system.

I want to know how many liters I’ve burned since my last fill up. So it would have to meter fuel supply to engine the meter fuel returned to the tank and do the easy math.

 

[ABMax24]

Did you try calling Steve at Firefish? That would be my first try.

 

[mclean]

You need to know while running or can you hand calculate every fill up at the pump?

 

[jcjc1]

Had a Floscan fuel flow monitor that I installed on my offshore boat back in my fishing/diving days.
It was one of those things that after the install, I wondered why I waited so long to get one.

 

[NoBrakes!]

that was easy...

 

[174mcx]

I need to be more clear. I have burn rate on my current gauges, however it doesn’t read volumes used... so I have no idea how much fuel I’ve burned since my last fill up.


I’d like to know that I’ve burned say 103 litres, 5 hours into my trip.

 

[NoBrakes!]

@Chrisco has been quiet lately, must be too busy having a time! He might know of such a device.

 

[pipes]

FloScan

https://floscaninc.com/wp-content/uploads/2022/10/4000-310-00-Floscan-FloTrac-Operation-Manual-Rev-A.pdf

 

[lilduke]

These things dont have a fuel guage?

 

[NoBrakes!]

I like that Floscan system, I like that other system that balances one tank to the other too

 

[NoBrakes!]

These things dont have a fuel guage?

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!

 

[lilduke]

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!

Ok, kinda like a sled. Funny that the ones in road vehicles work so well, but nobody else can figure it out.

 

[NoBrakes!]

Ok, kinda like a sled. Funny that the ones in road vehicles work so well, but nobody else can figure it out.

Like most things in life, the safe bet is to fill her up EVERYTIME lol just sucks when your boat holds 550 liters!

 

[174mcx]

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.

 

[S.W.A.T.]

I was always told if your concerned about burning gas you shouldn't own a boat unless it has sails

 

[ctd]

that was easy...

View attachment 284885

I must be missing something looking @ this. To the very left where it gives the scale color's & description, both engines state 3.4gph. The axis is ghp & 30 vs 45.8, WOT there not be a significant difference in fuel consumption....very little. Part throttle there would be a small improvement, nothing like this.

LSA engines are very good & make excellent power. The engine management system such as VVT & DI would make a small however noticeable improvement in part throttle economy. It takes fuel to make WOT power & the difference between the two would be small.

Then there is the headache with VVT, in a serious performance application I would opt out. I'm a fan of DI, not the same improvement as 2 stroke vs 4. Take a Ski Doo 800HO carb vs 800 ETEC, on the dyno WOT nearly identical gph or BSFC. Part throttle fuel consumption is significant between the two because DI helps clean up the mess of port timing vs piston position.

I hope I'm missing something in this article, it suggests significant reduction gph 6.2 LSA vs 6.2DI. The reduction in part throttle gph would be small & maybe noticeable. WOT would be very small.

 

[NoBrakes!]

3.4 is the impeller, the chart is worded weird for sure. On the same impeller, the two motors are pretty different. LSA's drink the fuel BIG time when you're in the boost....

 

[ctd]

3.4 is the impeller, the chart is worded weird for sure. On the same impeller, the two motors are pretty different. LSA's drink the fuel BIG time when you're in the boost....

That helps regarding the impeller. I still struggle with their claimed efficiency, it takes fuel to make power & WOT it is what it is. Part throttle it can make a difference.

 

[NoBrakes!]

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.

 

[ABMax24]

That helps regarding the impeller. I still struggle with their claimed efficiency, it takes fuel to make power & WOT it is what it is. Part throttle it can make a difference.

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.