Moving up from a small rib, fuel consumption advice.

[boatrusper]

Hi,
I currently have a Ribtec 535 with a 70 hp Evinrude, I will be looking to upgrade next spring to something like a Searay 215 weekender,(petrol engine) or a Fletcher 22 ideally with a diesel engine. Both trailerable .
I get around 4.5 miles to the gallon curently(1 Mile a litre) from mixed use, Itchenor to Chichester Bar at displacement speed, then a cruise at around 25 mph with the odd blast (35 mph) arriving at Bembridge, with a return eventually via Portsmouth back to itchenor, total distance of around 45 miles. which costs me 45x £1.37 =£61.65 plus the 2 stroke oil, so here's the question, will the Searay or similar use double the fuel? and how would a diesel Fletcher or similar fair in comparison.
I would appreciate any real world consumption advice that you may have to share, distance travelled, fair weather and fuel in cost used.
Regards Paul.

 

[gjgm]

I dont think you can micro cost.
You dont want a diesel in a small sportsboat;contradiction in terms.
For petrols, roughly
3litre 5 gph
4.3l 7 ghp
5.0l 10 gph
5.7l 12 gph
and you can probably increase those by 1/3 if you like tu push that throttle.
If you need to calculate fuel a 6 knots through Chichester harbour, you need to find a cheap hobby

 

[fireball]

If you need to calculate fuel a 6 knots through Chichester harbour, you need to find a cheap hobby

Try sailing!

Motor through the harbour @ 6 knots ~ 45 minutes to an hour ... so let's call it 3 litres ...

Raise sail and sail to Bembridge .... 0 Litres ..

Motor in - say 1/2 hour - 1.5 Ltrs

Double it for the return trip ... let's call it 10 litres .... nice'n'easy!

 

[jimmcgee]

MUM , MUM, THERE'S SOMEONE IN HERE TRYING TO UPSET US

 

[boatrusper]

Thank you for your replies, I am not looking to micro the cost through Chichester harbour, the cost is not particularly as issue but as posted, I am looking for a practical response in monetary terms. With reference to your 5.0l /10 gph are you saying that with petrol at around £6.31x10 gallons= £63.10 per hour? is this a likely cost for varied use an hour? or steady cruising speed?
What would be really useful would be a rough account of someones last cruise, weather, distance travelled, speed and fuel used, in order for me to account likely costs. I appreciate the sailing response.It would seem at present that I will possibly be trebling my current fuel cost?

Thank you.
Regards Paul.

 

[Nathan K]

When i was looking for my first boat i looked at a lot of bow rider/cuddys with 3 and 4.3 litre inboard mercruisers. Most the owners said an afternoon 3-4 hours cost around £60-100 pounds, depending on the particular boat. The 3 litres are your best bet if you want fuel efficiency. This was 90s engines however. If you’re looking at the newer inboards i know they have improved a lot. I’d say stick to diesel or LPG.
if you want to get some fuel figures for similar boats to what you are looking at check out boattest.com

 

[landlockedpirate]

The figures given are based on cruising speed, so to answer your question a 5L will cost about 2.5x your current usage and the 4.3L about 2x. As mentioned diesels in small sportsboats don't work, they are just too slow.

 

[[2068]]

Really not sure about the "too slow" thing with diesels.

A D3-220 is going to be a reasonable alternative for a 4.3 petrol.

I would accept "diesels on a small boat are too expensive and you'll almost never get the extra outlay back from reduced running costs".

 

[[2068]]

Thank you for your replies, I am not looking to micro the cost through Chichester harbour, the cost is not particularly as issue but as posted, I am looking for a practical response in monetary terms. With reference to your 5.0l /10 gph are you saying that with petrol at around £6.31x10 gallons= £63.10 per hour? is this a likely cost for varied use an hour? or steady cruising speed?
What would be really useful would be a rough account of someones last cruise, weather, distance travelled, speed and fuel used, in order for me to account likely costs. I appreciate the sailing response.It would seem at present that I will possibly be trebling my current fuel cost?

Thank you.
Regards Paul.

£60/hour would be for when you are at a "fast cruise", maybe 25kts.
If you focus too much on these kind of sums, you'll scare yourself silly and never buy anything.
Just add up roughly what you think you will spend for the year, divide by the number of smiles, sense of adventure etc, add on something for maintenance, then chuck away all the numbers, apart from that you can either afford to run a boat like this for each season, or you can't. The per hour thing is a bit of a red herring.

 

[gjgm]

Thank you for your replies, I am not looking to micro the cost through Chichester harbour, the cost is not particularly as issue but as posted, I am looking for a practical response in monetary terms. With reference to your 5.0l /10 gph are you saying that with petrol at around £6.31x10 gallons= £63.10 per hour? is this a likely cost for varied use an hour? or steady cruising speed?
What would be really useful would be a rough account of someones last cruise, weather, distance travelled, speed and fuel used, in order for me to account likely costs. I appreciate the sailing response.It would seem at present that I will possibly be trebling my current fuel cost?

Thank you.
Regards Paul.

The figures I gave you are typical cruising speed consumptions, but remember you might get places faster, so you "do" less hours perhaps. Also, you then picnic,swim,sit at anchor etc etc. so you arent buring fuel all day long.On the otherhand, if you waterski alot, you might well use even more.
Another estimate for a smaller sportsboat is 50 hours a year.
However, and its been a few years since I ran such boats, I never actually used anything like these fuel consumption figures, so I'd allow £2k for fuel for a good summer.
If you start pricing each trip, you'll never go anywhere!

 

[lovezoo]

I dont think you can micro cost.
You dont want a diesel in a small sportsboat;contradiction in terms.
For petrols, roughly
3litre 5 gph
4.3l 7 ghp
5.0l 10 gph
5.7l 12 gph

Bear in mind the EFI and MPI versions of those engines will give better fuel economy. My 4.3EFI in my 19ft boat uses roughly 1 litre per mile at a cruise speed of 20-30mph.

Also don't assume that a smaller engine will be more economic to run. The bigger engine option on my boat allows me to have a 19" propeller on the back, so the revs (and hence fuel consumption) are lower for any particular speed.

p.s. on this thread JHR says he is using not much more fuel than I am in his 21ft boat:

I have a 215, with the 5 litre efi engine. I reckon on getting about 3mpg at cruising speed (25 knots/3750 rpm). At maximum revs you can significantly increase that figure . I reckon on about 90 nautical miles per tankful in normal conditions but that's probably being a bit cautious.

I have a 5 mile trip down the Beaulieu River at 5 knots, before I can lean on the loud pedal, and I reckon that uses about 1 gallon.

I know I would say this, but they're cracking little boats. Excellent seakeeping for their size and great ride & handling. The cabin is, erm, snug, but better thought out than many of a similar size and - biggest plus of all - you don't have to lift the bunk to get at the loo: a great boon at 4.00 am . One side of the double bunk is longer than the other: I (6 ft) am OK - just - on the long side. Mrs jhr (5 ft 2) is OK on the other side but I wouldn't be.

You will give up before the boat does in bad weather but, in normal conditions, she's more than capable of doing Solent - Poole or Weymouth. Buy one, you won't regret it.

 

[landlockedpirate]

Really not sure about the "too slow" thing with diesels.

A D3-220 is going to be a reasonable alternative for a 4.3 petrol.

I would accept "diesels on a small boat are too expensive and you'll almost never get the extra outlay back from reduced running costs".

Agree with that as well, my comment was.directed at the boats the OP mentioned. Fletcher sports cruisers only available with 120hp Mercruiser diesel, which IMHO is not enough. I have only ever seen a couple of diesel Searays and they had KAD32 ( may have been re engined ?) Better than the Merc, but still heavy and underpowered for a sportsboat.

 

[gjgm]

Sure.. actually the OP might get some figures off boattest.com if its still about; at least for a similar boat.
But the consumption figures rise so steeply with that throttle that you can only give a benchmark.
As I said, I dont think I actually used that much, but it gives an indication perhaps of an annual fuel bill-that you can then write off your bank balance

 

[gpssti4]

I currently have an eighteen foot Fletcher (18GTS) with a 3.0 Mercruiser and allow about £2 a mile as a guide, that includes a bit of slow and a bit of fast boating. An afternoon out, say 3-4 hours, will cost £50-£60, but as most have said, don't worry about the fuel consumption otherwise you'll never use it.

 

[Scubadoo]

Don't know about petrol figures, however for my diesel on my 25ft boat, it does around 4.5mpg on average. The engine is a Volvo AD31 (150hp) and I cruise around 20knots.

If you looking at diesel then I would go for the KAD32 (170hp) which is the same block as the AD31 but with a compressor.

 

[paddy01]

Can't really advise per se but to add to the data you have available a Four Winns Liberator 201 with 5.7l V8 OMC King Cobra (270hp) will do a max of 2mpg on a good day. If we're having a proper play then <1 mpg.

That's fully fuelled and with 4 persons onboard

To be fair the engine and outdrive technology on that are quite old now so I'm sure newer technology would help.

Not sure it could improve on the sound of that V8 from the through hull exhausts mind you

 

[Jim@sea]

May I ask what your boat is. I have sold my (dreadfully slow) 21ft boat which had a 72hp Diesel but would only do 10 knots flat out, and I want a slightly bigger boat which will do over 15 knots as from Whitehaven I can see the Isle of Man and I want to do it in 3 hours.