Fuel cons - merc 115 - RPM?

[cooky]

curious. This 115hp Mercury 2 stroke (2001) I've got on my new (2nd hand) boat - I think the fuel tank is 100 to 120lt and I am looking at getting another fuel tank to possibly double fuel storage in the boat.

I was just curious (new to this) as to what should be the average fuel consumption (lt/hr) and what is the most efficient cruising speed. ???

the other week around the Palm Islands I had it at around 3800 - 4000 rpm 90% of the time, however it felt most comfortable at around 4200 / 4300 rpm. Would there be much difference in fuel economy?

The fuel gauge is flicking all over the place (I need to fix) so hard to tell useage at present, although it seemed to use over 50lt from Taylors Beach to back of Palm Islands and back (half way to reef).

I carried 2x25lt extra fuel containers in the boat for safety, but this isn't ideal obviously.

I'm asking because I'd like to head out to the REEF on good days and want to make sure I've enough fuel.

[aido]

The fuel gauge is flicking all over the place (I need to fix)

good luck fixing that cooky.
i reckon about 1.5 km/ltr might be about right for your rig.
fuel consumption is always a worry, put your mind at ease
and get a navman fuel flow meter.

[drb]

A fuel guage is never real accurate in a boat due to list, trim etc. Have heard good reports about the navaman gar once they are callibrated correctly.

many things affect your fuel consumption such as trim (have a play with you power trim while running on smooth water and you will be surprised at the difference it can make on speed and revs) and water conditions. My advise is to have as much as you need for the trip + half again for unforseen events.

[cooky]

i know about the navman fuel meter, but don't you have to have a navman sounder or gps to connect it to?

[drb]

I think you can also get a seperate unit to display fuel info. it is in the navman catalogue I got at the boat show. Try http://www.navman.com/marine/products/fuel/fuel3100/index.html

[reeldreamer]

Hey i have a 18month old 6m Signiture which had a 150efi merc we have just changed it to a 175optimax with smartcraft guages and the new navman fishtracker 6600. We have discovered that the best crusing revs are around 3600-3900 rpm which is about 25-27kt =-1.9l per 1km, ihope this helps :-/

[whiteman]

Cooky

My 115 2-stroke Yammie on a 5.3m Qunnie gets 1.7l/km at around 4000. Doesn't vary too much if I get up to 4300 but over that it starts to chew fuel. The Navman fuel flow meter is brilliant. I too work the Palm Islands and I'll have to carry fuel canisters for reef work. No problem with this if you empty them when there is room in the main tank rather than when they are needed (ie use them on the way out!). You can always call into Palm Island if you run short :D

[cooky]

thanks Whiteman - stop in for Blackman at Palm.

didn't know you could get fuel there. Good point. Was my first time around palm the other week.

Thanks for the comparison - they should be similar - particularly if yours isn't that old.

I have room for another underfloor tank, so am going to see how I go. Getting fuel in the tank at rest when flat is challenging enough let alone in rougher water :P.

Although I guess if the cost is high I'll just use my brains ??? and buy some fuel line and some sort of handpump - the fuel entry point is easy to access, so could work really well. That way I can always buy more 25lt fuel containers and if I need to go for a quick trip to say New Zealand I'll just fill the boat up with them........ 8)

[drevil]

Hey Reeldreamer

What's the 6600 like? #Thinking about getting one as well.

[craigie]

Cooky,

My 115 Merc Opti gives approx 2.3 k's per litre when averaged out.

Also uses about 18 litres per hr around 4000 revs doing 24 knots on a light/medium weight 17 footer (Cyclone 540)

These figures may vary a bit to yours but will still give you somewhere to start.

Regards
Craigie.

[Payneful]

Use a siphon hose (the ones you shake up and down to get it started, has a marble inside) to transfer the fuel from your drums into your tanks, beats wasting half of it in the boat and polluting the water! A slightly more practical but expensive idea is to use portable fuel tanks with the fittings and just plug them onto your motor when they are required.

Sam.

Sam