Fuel Usage Rate ... small Rib

fireball

New member
Joined
15 Nov 2004
Messages
19,453
Visit site
We run this rib for our club racing as a patrol boat. It is always in the harbour and normally the rib just potters along at 4-5 knots then sits around not doing much. Very occasionally someone provides some sport and has a suitable capsise that warrants a rapid response from the Rib to ensure the recent occupants are still alive.

We are doing a little outing - which will involve going outside the harbour /forums/images/graemlins/blush.gif ... but how much fuel should we allow for? I don't suppose the rib will be out that long - 4hours max? but we need to ensure we've got enough just incase it ends up towing the fleet back ... so could do with a rough guide to fuel use per hour ... I know there will be a significant difference on/off the plane ...

The rib is: Ribcraft 5m rib, 2 up, Honda 50hp 4stroke, 25L tank.

Is that enough fuel or should we take extra cans? We have 3 x 5L cans we use to top up the main tank when ashore.
 

duncan

Active member
Joined
16 May 2001
Messages
9,443
Location
Home mid Kent - Boat @ Poole
Visit site
engine can consume around 4 gph at wot so on the one hand the safe assumption is about an hour!

more realistically I would suggest 1.5gph as an estimate but this is really a guestimate as it will vary hugely by the use of the throttle. I used to head out fishing with a 90 2s and 2 x 25l tanks and that worked fine with a few miles run and a few hours at anchor........

You don't mention how far from base you are heading - I would suggest a much better 'plan' would be to carry sufficient spare fuel to comfortably and safely get you home and then 'use the throttle sparingly' over the on station piece. 5l will give that boat about a 15mile safe passage in good conditions (80% range at 15 knots estimate)?

All theoretical and extrapolated etc......
 

fireball

New member
Joined
15 Nov 2004
Messages
19,453
Visit site
Thanks Duncan ... it's max 2 miles off shore, and the whole trip would be 20Nm as the crow flies ... but we all know powerboaters ... can never go straight there ... they have to zip off here and there, never holding a straight course! /forums/images/graemlins/tongue.gif I think all 3 5L cans will now be filled and carried ...
 

fireball

New member
Joined
15 Nov 2004
Messages
19,453
Visit site
Ah - you see - I'm one of those that uses the renewable source of fuel ... wind ....!! No - not the bakedbean sort! /forums/images/graemlins/blush.gif

The course takes them max 2 miles offshore, but it is a 2 mile leg and the boats won't be sailing at the same speed, so they'll need to spend some time out there ... and then they'll have to find the big boats for their tea/coffee supplies ... so generally want to make sure they won't need a tow back in! /forums/images/graemlins/blush.gif
 

fireball

New member
Joined
15 Nov 2004
Messages
19,453
Visit site
Funnel??!! Na - we've got a filler pipe - screws into the top of the fuel can ...

Thanks for all the input!
 

Giblets

Well-known member
Joined
5 Mar 2006
Messages
9,254
Location
Surrey
Visit site
Did exactly this in my Ribcraft 4.8 with a 50hp Mariner 2stroke on the back at the school's sailing club regattas from HISC. 25l was more than enough for a days running but I always carried 1 x 5L as well.

BTW, suggest one of those jiggle syphon tubes for transfering fuel - far safer than trying to upend a can in a good chop.
 
Top