Fuel Usage

[skinnylegs]

We have just completed our first family trip out on the boat (Sealine F33), Eastbourne to Yarmouth for three days and then back to Eastbourne. Nice place Yarmouth with some new experiences for us.

Firstly mooring between piles, thinking back I didnt remember this on my Day Skipper course. Anyway all went well and the Harbour master assisted with the ropes etc. Then secondly it dawned on me that there was no where to plug the shorepower, This really was an asset as no TV etc made for a peacefull few days.

Back to the question, Before leaving Eastbourne I filled up Both tanks and they read Full on both gauges. When we arrived at Yarmouth one tank read three quarters full and the other tank under a half. I have checked all the fuel taps are in the correct position as per the manual so that both tanks are used and that the returns should go back to both tanks. Could one engine be burning that much more fuel than the other.? Are there any other possibilities that I have overlooked.?



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[PhilF]

don't suppose the heater was on, our always reduced evenly except for the heating.
were both engines pulling the same revs, have you got mercs or volvo's

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[skinnylegs]

The heating was switched off.

We have Merc's and the Revs were identical during the passage.

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[DavidJ]

Did you fill your tanks to overflowing (the breather) or just to max level on the guage. The only way to really tell if somethings up is to fill to max, have a good weekend say for a couple of hours then fill to max monitoring what goes into each tank.
I know that my Sealine doesn't breath too well on filling so the pump can 'click out' when it's not really full. So when filling go real slow at the end to ensure you have a good fill in each tank.
The full guages, like a car guage, will read full before it is actually 'fully' full so my guess is that you started off with one 'fully' full tank and one 'just full on the guage' tank
David

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[PhilF]

guage might be dodgy
fill em both up and see it the same amount goes in each.
I have some spares, pm me if you want a list

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[adarcy]

<<Could one engine be burning that much more fuel than the other.? Are there any other possibilities that I have overlooked.? >>

Certainly either or both are true.

It rather depends on how long you've had the boat and how much you know of the engine burn rate (ie they may have the same revs showing but the boat veers unless steered so one is pushing harder and will take more fuel)

Most likely it is the return fuel flow though. Diesels pump and filter much more than they need and return the excess to the tanks (which is why they're warm after a long run). "Most" boats have a balance pipe between the tanks which may or may not allow them to level out but also many have a balance pipe which, according to the way the taps are set, will put the return back into one tank only or a balance between them. In our boat the port return valve has to be 1/3 closed otherwise we get exactly your symptoms (oh and the gennie and heating can complicate the issue).

There have been a couple of posts recently about fuel pipe layout which I am sure you can find (if you can think of suitable search terms)

Found it

F33 Fuel tank useage posted by Roy on 30/6/04 - suggest v useful for you and would have saved me typing so much

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[skinnylegs]

Thanks for the advice and will have a play next time out on the boat.

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[hlb]

Quite possible that one engine is using far more fuel than tother. Rev counters are not that reliable. My upstairs counters record compleatly different from downstairs. Last boat was the same. I just juggle the throttles til I get same fuel usage. About 2200 on port and 2800 starboard, well thats if I'm upstairs. Down stairs seems about right!

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