Beta 20hp fuel economy

Ru88ell

Ru88ell

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Somewhat incredibly, after a few days staying on my trailer sailer, my wife suggested we get a bigger boat. I expected this process of enticing her into more serious boating to take at least another 5 years, so a great result!

So, I'm currently using a Mercury 6hp outboard which used about £8 of fuel over our fortnight holiday pottering about in Falmouth/Helford. The boats I'm looking at displace 3500kg, and one has a brand new Beta 20hp 3 cylinder engine. Does anyone have an idea what the hourly fuel usage could be for that at 5kts? I'm guessing more than my outboard.

I'm usually the first to get the sails up, and regard motoring as a fail, so would only really use it for mooring. Obviously, a bigger boat would lead to me taking on longer passages on which I could get caught out and need to motor some distance. I currently have no idea how much fuel these things use.
 
Had some coffee and checked the figures for my boat - Stag 28 with displacement of 3,500Kg, fairly easily driven hull. Engine is 13hp Volvo and consumption average is about 1ltr/hr (just over). I would estimate I'm using about 10hp to drive it along at about 5knts in average conditions.

Looking at the graph - this one is a bit better :-

http://www.betamarine.co.uk/seagoing/beta20/B20_Tech_Photo_Sheets/B20-SDS-0311.pdf

It shows 1ltr/hr consumption at 2,200rpm where it's producing about 13bhp, so macd and vyv seem to be spot on.
 
Between 1 and 1.3l an hour. Fuel consumption on small diesels is pretty consistent. Typical annual engine hours on a weekend sail basis is between 100 and 150 hours a year so with a typical tank of 70l you use less than 2 tanks a year.
 
Sadler 34, Bukh 24 ~ 1lph in and out of marina / picking up mooring > 1.5 lph motoring ¾ throttle 6knts.
I too get the sails up asap and kill the donk - the eberspacher burns far more fuel than the engine - about 1l every 4 hours or 6 liters per day - SHMO does like to be warm.
As others have said - forget the diesel bill - it is minimal compared to other running costs, unless you have a MOBO that is, in which case>

FuelishWallet.jpg
 
It's damn all to do with the engine!

I don't disagree with any of the helpful comments above, but note that all modern diesel engines, be they 6 or 6000 HP, consume pretty much exactly 0.3 litres per kWHr used. Thus consumption depends on the boat and, very strongly, on the speed you motor at, but not on the engine.

Thus people's practical experience in similar size and style boats is highly relevant whatever engine they have.
 
A rough rule of thumb i used to use for bigger diesel engines was.. hp divided by 4.. so a 200HP diesel at MAX revs would use approx 50lts per hour.
so your engine will produce 20hp at max revs so = 5ltrs per hour..so unless you plan to charge around at full revs all day i would reduce that consumption by 1/3.
hope that helps.
 
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chrishelen said:
A rough rule of thumb i used to use for bigger diesel engines was.. hp divided by 4.. so a 200HP diesel at MAX revs would use approx 50lts per hour.
so your engine will produce 20hp at max revs so = 5ltrs per hour..so unless you plan to charge around at full revs all day i would reduce that consumption by 1/3.
hope that helps.
Click to expand...

I can't relate that to my experience with a Prima 50. On that basis: 50 /4 = 12.5 litres per hour, reduce it by 1/3 so say 8 litres per hour. Over the last decade plus, my engine has averaged 2.55 litres per hour and when it's running, I tend to work it quite hard......
 
chrishelen said:
A rough rule of thumb i used to use for bigger diesel engines was.. hp divided by 4.. so a 200HP diesel at MAX revs would use approx 50lts per hour.
so your engine will produce 20hp at max revs so = 5ltrs per hour..so unless you plan to charge around at full revs all day i would reduce that consumption by 1/3.
hope that helps.
Click to expand...

My rule of thumb is 1 lph per 10 hp (used - not nominal).
 
chrishelen said:
A rough rule of thumb i used to use for bigger diesel engines was.. hp divided by 4.. so a 200HP diesel at MAX revs would use approx 50lts per hour.
so your engine will produce 20hp at max revs so = 5ltrs per hour..so unless you plan to charge around at full revs all day i would reduce that consumption by 1/3.
hope that helps.
Click to expand...

Not relevant to engines in displacement boats. The amount of power produced depends on how much the prop is demanding. So at cruising revs (around 2500 on the beta in question), the prop is only demanding around 8-10hp even though it is capable of producing 15 at those revs. The governor adjusts the fuel to keep the required revs for the speed, as it is the speed of the prop that moves the boat, not the power produced by the engine.
 
Consumption on a Beta will not be a problem, what will be a serious ball ache will be the price of service items and spares. Some friends of mine were quoted over £300+vat for a gasket set for a 13hp(?) 2 cylinder engine and yes they are different to the equivalent plant bits.
 
I didn't find the cost of spares on my Beta 20 to be exorbitant - I didn't need to change the head gasket or anything, but oil and diesel filters seemed OK.

Neil
 
Tranona said:
Not relevant to engines in displacement boats. The amount of power produced depends on how much the prop is demanding. So at cruising revs (around 2500 on the beta in question), the prop is only demanding around 8-10hp even though it is capable of producing 15 at those revs. The governor adjusts the fuel to keep the required revs for the speed, as it is the speed of the prop that moves the boat, not the power produced by the engine.
Click to expand...

I said a Rough guide...better to over estimate don't you think?
 
chrishelen said:
I said a Rough guide...better to over estimate don't you think?
Click to expand...
Not really when you can get pretty accurate fuel consumption figures. Your "estimate" leads to consumption more than twice the most pessimistic real figures. In other words if you use your estimate to calculate range from a tankful (the most useful estimate) you will be looking to refuel when your tank is still half full.
 
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