Floscan fuel flow meters

[boatmike]

Does anyone know of a UK supplier or do I have to go direct to Seattle?

Navman used to sell Northstar ones but they have gone bust it seems.

Anyone know of a competitive product or are Floscan the only alternative?

 

[Bassplayer]

If you have a Garmin plotter you can use their GFS10 sensors. Failing that try Mike Belamy at Lancing Marine.

 

[Latestarter1]

Does anyone know of a UK supplier or do I have to go direct to Seattle?

Navman used to sell Northstar ones but they have gone bust it seems.

Anyone know of a competitive product or are Floscan the only alternative?

UK Distributor in Poole http://www.merlinequipment.com/

Flowscan stuff works, but is not cheap.

 

[boatmike]

Thanks for that. Got quote from Merlin at £1,600 for a twin engine set up that will interface with GPS and readout litres per mile. I believe with the price of diesel on a vessel with two TAMD 41 Volvos, knowing what the most economical speed is for any given wind or tide condition (and that is not necessarily as slow as possible) will save me this over about 2 years of usage. It will also give me an instant alert to any problems (injectors,fuel contamination, nick out of prop, dirty bottom etc) and tell me both engines are in a good state of health.... How much is that worth??? Don't really understand why more owners don't fit them with the current price of diesel. It would certainly answer the question asked on another thread regarding running on one engine or not instantly....

 

[Bassplayer]

I use 2x gfs10 Garmin fuel sensors at about £140 each with a Garmin 750 plotter. You get a reading for fuel in and out for one engine, so you take one figure from the other and get a litre/hr or gall/hr figure then against speed get an mpg figure, doubling up for 2 engines. I found on my boat that 18-25kts it does 1.7 - 1.9 mpg, but 4mpg at 15kts!
This set up whilst needing a little arithmatic is a bit cheaper than what you have been quoted for and you have thebenefit of a great plotter!
Let me know if you want any more info or want to see the setup.
Paul

 

[PCUK]

NIce idea Bassplayer!
But you'd think Garmin would have the sense to provide a program that did it for you. They don't seem to like these new fangled diesel engines!

 

[Robin]

Bassplayer's solution is at least affordable if you have Garmin stuff anyway. We have Garmin on our new to us mobo in the USA so will keep that in mind as an option.

Otherwise what I plan to do is to chart engine revs versus speed and consumption and engine hours run. Time consuming but can always be done over a month or two, in our case by running both engines on one tank filled and then refilled after a reasonable run at constant revs. Speed (boatspeed not GPS SOG) v rpm will vary with conditions I know but fuel usage at constant revs should be the same per hour regardless. Thereafter we will have a good idea of expected consumption if we take the worse case scenario of average revs used throughout a trip, ie assume all the journey is at cruising revs even though less would have been used in places like entering and leaving harbours.

The only, but potentially significant, confusion is how much additional fuel is used by the generator, since many in the USA where our boat is will run their generators for the aircon and cooking. In our case we have big 440W solar panels plus 160A alternators on both engines and can run most loads (fridges, freezers and icemaker all both 12V DC and 110VAC) underway without the generator and cooking is by propane. Anyway a separate fuel usage chart v engine hours can be created the same way.

 

[oGaryo]

I have a Navman fuel flow thingy on my boat but to be honest, it takes away the enjoyment, for me, so I don't use it.. instead, I put enough go juice in the boat to make absoutely sure I'll not run out of it for whatever I have planned that weekend and just enjoy the boat doing whatever feels right with the throttle, tabs etc set to get best speed for lowest revs which should then give me the best ride possible and by default, the most efficiency/economy... don't get me wrong, I can't afford to burn money wastefully but life's too short to worry about it to the extent of altering the way I use the boat.

 

[Latestarter1]

NIce idea Bassplayer!
But you'd think Garmin would have the sense to provide a program that did it for you. They don't seem to like these new fangled diesel engines!

Cos new fangled diesel engines have no need of add on bits, fuel consumed plus other bunch of engine data already available down the datalink........

 

[Robin]

I have a Navman fuel flow thingy on my boat but to be honest, it takes away the enjoyment, for me, so I don't use it.. instead, I put enough go juice in the boat to make absoutely sure I'll not run out of it for whatever I have planned that weekend and just enjoy the boat doing whatever feels right with the throttle, tabs etc set to get best speed for lowest revs which should then give me the best ride possible and by default, the most efficiency/economy... don't get me wrong, I can't afford to burn money wastefully but life's too short to worry about it to the extent of altering the way I use the boat.

Bit different if your plans involve more than a quick blast or two round the bay. In our case our boat is in Florida and we will be going south out to the Bahamas or beyond in one direction and north up to Chesapeake in the other. Filling stations are not conveniently placed every 5mls and being able to plan properly means having some idea of the ranges possible at different revs/speed.

 

[grumpy_o_g]

I have a Navman fuel flow thingy on my boat but to be honest, it takes away the enjoyment, for me, so I don't use it.. instead, I put enough go juice in the boat to make absoutely sure I'll not run out of it for whatever I have planned that weekend and just enjoy the boat doing whatever feels right with the throttle, tabs etc set to get best speed for lowest revs which should then give me the best ride possible and by default, the most efficiency/economy... don't get me wrong, I can't afford to burn money wastefully but life's too short to worry about it to the extent of altering the way I use the boat.

What you need is a meter that is calibrated from "When it's gone, it's gone" through "That's a good compromise" to "Whoa, you're really saving money now". If you had an analogue gauge you could just change the dial face.....

 

[boatmike]

That's incorrect. You can run at 1500 RPM under no load and the fuel used will be minimal. 1500 RPM under maximum load will be significantly more. Variations between these extremes will be considerable.
You are correct in assuming that speed over the ground will change at constant RPM with say tide, wind, and other factors so that at a given RPM the load will change which affects litres per hour, but then the distance covered will also change in that hour making your calculation regarding the most economical speed variable too. It's frankly not as simple as you suggest and my belief is that a constant read out telling you what your fuel consumption is in litres per mile rather than litres per hour is invaluable. Very often the most economical speed can in fact be to go a little faster especially with a headwind and tides against you.....

 

[Robin]

That's incorrect. You can run at 1500 RPM under no load and the fuel used will be minimal. 1500 RPM under maximum load will be significantly more. Variations between these extremes will be considerable.
You are correct in assuming that speed over the ground will change at constant RPM with say tide, wind, and other factors so that at a given RPM the load will change which affects litres per hour, but then the distance covered will also change in that hour making your calculation regarding the most economical speed variable too. It's frankly not as simple as you suggest and my belief is that a constant read out telling you what your fuel consumption is in litres per mile rather than litres per hour is invaluable. Very often the most economical speed can in fact be to go a little faster especially with a headwind and tides against you.....

Over the last 24 years (so a good sample period tested!) on two different sailboats and 3 engines (one was replaced) and 2 different fixed 3 bladed props and one variable pitch one I think I can trust what I said.

We used to always run at constant engine revs once we were motoring. On a Westerly 33 Ketch with a 4 cylinder 42hp Mercedes OM636 2000 revs gave a constant fuel usage of 0.62gph, time after time after time. We switched the engine to a 4 cylinder 50hp MD22L with a different 3 bladed fixed prop and the consumption at 2000 rpm was 0.55gph, time after time after time. The next boat a 41ft Sun Legende with a 4 cylinder 44hp Yanmar 4JHE but fitted with a Brunton Autoprop run also at 2000rpm gave 0.53gph time after time after time. The boatspeed through the water in all cases varied with conditions of wind and seastate but the gph figure if we kept steady revs was constant despite varying loads Of course if we upped the revs to keep the same boatspeed then the fuel consumption increased.

I have an American book about cruising under power which quotes the fuel figures for a trawler yacht that crossed the atlantic, in a table that relates rpm to speed to gph. So I'm not alone in thinking it works!

I would love to have Floscan on board, but the price of installing it on 2 engines and a generator would buy a whole lot of fuel, whereas the tabulated figs cost nothing but time to produce. Just my tuppence worth.

 

[boatmike]

Well I won't make this a competition Robin but as a Chartered Mechanical Engineer I stand by what I said both in theory and practice. With the vessels you quote, with relatively small engines, you will be approximately the same within practical purposes with the vessel under normal load in terms of litres per hour burnt assuming the load conditions are relatively constant, but this will vary considerably in terms of litres per Nm where conditions, as you said originally, will affect the distance covered. You will find that if (as in my case) you are proposing running two 200HP diesels and cruising extensively, the most economical speed will not always be obvious because conditions will vary and it is simply not easy to estimate the most economical speed by considering RPM alone. While I have spent most of my leisure hours around sailboats myself over a period of some 40 years (yes I am that old!) my professional career has been related to far larger power driven vessels where Floscan equipment is used far more extensively. It these cases owners and skippers alike are very interested in running at the most economical speeds and if it was as simple as just checking RPM they would not fit computers on the bridge to calculate it for them. Within the leisure market owners of TSDYs with the high cost of diesel at todays rates should consider it too in my opinion as the payback period would be relatively short, but I would not suggest it for everyone, it's up to individuals to consider their own priorities. If you have a bottomless pocket you might not care. Also if you only use your boat for occasional short trips it might not be justified. The fact though is that RPM is simply NOT a measure of fuel burn on it's own, otherwise a diesel running at 1500 RPM under no load would consume the same as one pulling say 100HP at the same RPM. Fuel burn on a diesel is usually quoted as grammes per Kilowatt/hour and is usually in the region of .2 to .25. This will vary for a given engine through its designed range of RPM and usually minimum at approx 3/4 throttle. To calculate the predicted total burn therefore you multiply power by burn rate for a given RPM.
But hey, I don't presume to tell you what to do. Thats your decision, and for your circumstances your approach may well be near enough right to make no difference. I just thought for others sake I should point out that its not as simple as that. Its also interesting that often the most economical speed is faster than one would assume, which is sometimes nice to know!

 

[Robin]

I don't think we are really disagreeing here Mike. The reality is that under average conditions with the boat in gear and moving and the same prop, there will be a correlation between fuel burn per hour and engine revs. I agree it would be completely different under no load but then with the engine in neutral and no load the distance/speed travelled will be the same at any revs, precisely zilch. The prop load may well vary with headwinds versus tailwind loads and seastates but overall over time the variations will smooth the answer to be usable as a base figure to use, to which a safety factor can be added under bad conditions perhaps.

Our new (47ft) boat has twin 250hps. I have the fuel logs over a recent 3 months Bahamas cruise at speeds between 7.5 and 9kts and including some generator use and the average works out at around 3.57gph (US gallons, so 13.2lts/hour total). The boat can do 17.6kts (we did that on seatrials with a dirty bum) but I dread to think of the consumption then. What I'm proposing to do is to get some figs tabulated from different revs in calm conditions and speeds below and up to hull speed, or maybe even later to up the revs to get to say 12kts out of curiosity, but we will aim to run at displacement speeds mostly.

Like I said I would love to have Floscan, but the costs are high. They may be justified in fully planing boats that are cruised at full planing speeds, but in our case where we are really semi-displacement I think the situation is different.

For information these are 'real world figures' as quoted in Stapleton's Powerboat Bible for a 58ft Hatteras with twin Detroit N-71 naturally aspirated diesels, on an actual transatlantic cruise:-

RPM Boatspeed S/L Ratio GPH (Lts) MPG (nm/L)

1400 8.3kts 1.15 6.6 (25) 1.25 (0.33)
1500 8.5kts 1.18 8.5 (32) 1.0 (0.26)
1800 10.7kts 1.48 12.0 (45) 0.80 (0.24

This is akin to what I want to tabulate for our boat.

 

[vas]

I use 2x gfs10 Garmin fuel sensors at about £140 each with a Garmin 750 plotter. You get a reading for fuel in and out for one engine, so you take one figure from the other and get a litre/hr or gall/hr figure then against speed get an mpg figure, doubling up for 2 engines. I found on my boat that 18-25kts it does 1.7 - 1.9 mpg, but 4mpg at 15kts!
This set up whilst needing a little arithmatic is a bit cheaper than what you have been quoted for and you have thebenefit of a great plotter!
Let me know if you want any more info or want to see the setup.
Paul

was checking the options and it appears that GFS10 stands for Gasoline Fuel Sensor 010-00671-00. Do you indeed use that on a diesel engine? No problems with that?

cheers

V.

 

[boatmike]

was checking the options and it appears that GFS10 stands for Gasoline Fuel Sensor 010-00671-00. Do you indeed use that on a diesel engine? No problems with that?

cheers

V.

Very big probs with that actually as you require 2 flowmeters for a diesel. One for flow, one for return. One minus t'other = burn rate. Not so on Gasoline where one meter would do.

 

[boatmike]

Fine Robin, and I agree that if load is the same there will be an approx correlation. I think you will find more variation on your TSDY though than you are used to on a sailboat but it's entirely a matter of choice to fit flowmeters or not. The last boat I skippered with large diesels was in fact a Feadship which was 46 metres OAL. It was indeed equpped with Floscan which is when I became a fan. Running at 14 Knots rather than 12 on a delivery trip from Oslo to Cannes actually saved about 10% in fuel which was a total surprise and the savings would, in this case,have bought me a new system 3 times over! Without it I would have run slower to conserve fuel and been quite wrong.....
I shall certainly fit a system to my Aqua-Star 33 when I get it but not just to conserve fuel. It will also give me a good early warning of any problems. Injectors, fuel pump, leaks, claggy filters, dirty bottom, transmission problems, propellor fouling etc. all show up initially as variations in fuel burn rate. It's therefore a fabulous indication of total health as well as telling you how to get the most out of your boat. As I said before though it's a matter of choice and a non essential item so if you choose not to have one I wouldn't argue.

 

[Robin]

I just looked again at prices and for us at Floscan factory price direct in the USA it works out at about $3,400 inc sales tax for a two engine set or about half that for a single, in each case not including the generator and not including installation costs. At current Florida prices that is more than 850 gallons worth of diesel. If we cruise 1600mls per year say at 8kts we expect to use around 800 gallons so if we saved 10% of fuel it is 10 years to recover the cost. If we fitted a system to just one engine and simply doubled the figs it would still take 5 years to repay.

Am I looking at the right prices thereabouts?

Might be academic anyway in our case as Irene seems to be headed straight towards our boat...

 

[boatmike]

Robin.

They are expensive, but I was quoted £1588 plus VAT from the agent in Poole for a twin enging system that will link to GPS and give me litres per Nm. There are lots of choices in their range and I think you are looking at a single engine unit and doubling it.
My calculation is based on living on board and using more fuel per annum than you. Thats why I was careful to say it's up to each one to decide if it's worth it.
Good luck with Irene!