Best RPM for fuel economy

[dreemon]

Hello all, I finaly fitted my revometer to the tinny and would like to know what rpms are best to get the most outa the tank on a longer trip, my manual says wot is 5500 rpm, I know the bigger motors have fuel managment to help save fuel , I'm just after an average rpm that will save on petrol, cheers,

It's on a tiller, heres a pic,
http://i10.photobucket.com/albums/a105/JerahsRainbow/boatconsol09_08.jpg

[BaitThrower]

Lots of variables. Can be worked out but results would vary on conditions and a million other possible factors.

I would just say, get boat on the plane, then run at the lowest RPM that keeps it comfortably on the plane. That would give you a good starting point as to best fuel economy for distance.

[Vitamin Sea]

Very generally, less than 4000

Cheers

VS

[disorderly]

Lots of variables. Can be worked out but results would vary on conditions and a million other possible factors.

I would just say, get boat on the plane, then run at the lowest RPM that keeps it comfortably on the plane. That would give you a good starting point as to best fuel economy for distance.

Yeah too many variables...but realistically as baitthrower suggests...just get your boat up on the plane and cruise along......

Oh... and Morgans make a beaut 3.5% midstrength (going by the red can in your boat)...home brew will save you more in the long run than the fuel you use....

It does for me,anyway.::););D

Scott

[Hornet Rider]

dreemon, that's a neat little setup you've constructed with your sounder, tacho, switch panel, compass & radio. Just a question? Is the compass influenced by the close proximity of your hand-held?

[krazyfisher]

at a guess 3900-4200 should give you good all round fuel figures l/per hr and maybe 4800 for the best l/per klm. no real science but out of 3 boats I have had fuel flow meters on about 72-75% of wot give the best results. this is just what I have found....

[FNQCairns]

Yeah like Krazy says.

The equation is a sliding one. L/H is almost a wasted statistic when on the water, it's great for the showroom though.

The end result will be the slower you go when on the plane proper the less L/H you will use....although most often the distance travelled on any L of fuel will plummet.

There is a sweet spot and it will depend on every aspect of your particular rig and setup.

Mine for example uses the same total amount of fuel to get to where I am going at both 3500rpm and 4500 rpm, obviously I prefer to travel at 4500 if possible.

I travel the longest distance per L at around 4300 but of all above use the least planing fuel per hour at 3000 to 3200rpm.

The above slides somewhat with an extra body on board or the fuel tank is empty etc, to get the best you need a fuel gauge as conditions change...none the less on most 2 strokes a steady set throttle 4000-4200 can be a good guess to maximise range, most especially on light boats, heavy boat often need more rpm than this to find the sweet spot.

cheers fnq

[Angla]

I would say that I get the best constant results between 3800-4200 if you do not alter the throttle. I've found that when you sit with your hand on the throttle and make adjustments all the time then the fuel use is terrible. Try to set the throttle to the conditions and concentrate on steering with both hands.

Cheers
Chris

The setup looks great with the tacho and all the good bits. Job well done.

[dreemon]

Thanks guys, Disorderly, yes I recon the home brew would be a Very wise investment, guess no one took it for a can of coke,

Hornet rider, the uhf handheld doesn't seem to bother the compass but does interfere with the sounder only when theres talking on it, the rpm gauge had to be at that height as it would make changes when it was close too, but I have a handhed gps mounted up a bimini pole,

FNQ, Angla, sounds right holding a constant speed to get more outa the fuel on the longer trips, 4500 should travel well,

For the box, It started with a glovebox from whitworths $45? then housed it with t&g hardwood flooring, originally it had 2 drink,holders, the 4 gang switch panel fits right in it , and added the cig lighter , then just a matter of wiring, but it is locking and good to keep wallet, mobile and smokes dry

Cheers :D and thanks !

[castlemaine]

Don't know how accurate but I was told to check speed vs revs. If I was doing 25 knots and increasing revs does not increase speed appreciably then I'm wasting fuel, so reduce throttle till you reduce your revs but still ataining the same speed. Cheers 8-)

[cormorant]

You'll only get good fuel ec if it is propped right to start with. Check you are getting 5300 at wot with a regular to heavy load on board and then what is said in the above posts is right. If you can't get 5300 wot you will be overloading the motor and shortening it's life significantly.