Cruising performance

Collenan · 05 August 2018, 06:46

Hi, I'm new to RIBs but not to boating as we sail as well. Recently bought a 2008 XS RIB 600 with 2014 Yamaha F100DET fitted as a runabout in the Clyde and to get to our yacht mooring. I know max RPM is 5-6k but what should cruising RPM be on this and likely performance/fuel economy? Any thoughts?

Last Tango · 05 August 2018, 08:35

Cruising speed is really down to sea conditions and how much petrol you want to burn.

I've got a slightly bigger boat and engine but I generally find 24-25kn is a good cruising speed, engine's at about 3400rpm and burning around 0.7 - 0.8 litres per nm.

You're gear ratio will probably be different but I'd think same speed @ 3.5 > 4k RPM. and marginally better fuel consumption.

Others with a more similar outfit will be able to nail the figures down a bit tighter and there'll be other opinions re. cruising speed but that's what I aim for to optimise my range. 100nm+ in a day is well within scope.

Bern Hanreck · 05 August 2018, 08:55

I agree with your estimated revs but it will also depend on what prop you have and how heavy or light you generally run . Every set up is slightly different and conditions are infinitely variable but most of us wouldn't run at full chat , other than to find out what she'll do

. Sometimes a few hundred rpm less can make a distinct noise reduction which most ( not all ) people prefer .

I used to get ( Ribcraft 5.85 with your Yammy F100 ) a top speed of 33/34 knots . I always reckoned on 1 litre of fuel per nautical mile consumption , but in prolonged good conditions often did a bit better . She would cruise all day at 25 knts , but how often are conditions that good in the Clyde ? Enjoy your rib and stay safe .