MPG or GPH

[askipper3]

What unit would be the best bang for buck> and tell me what i need to know when it comes to best overall fuel consumption?

[76Red18]

The 310 or 3100 shows real time fuel economy so you can actually see the the best throttle setting. These units have to be interfaced with a tach and gps or something else that gives speed info. The lesser priced units 210 or 2100 only show fuel consumption, gallons used per hour. With that info you would have to keep track of speed and rpm and do the math yourself. PITA

[76Red18]

web page

web page

couple os sites, looks like navman and northstar are the same unit with navman being a bit cheaper

[Ikan Besar]

I've been very happy with the Floscan unit on my 20'.

[Fr. Frank]

I went cheap, and bought a Navman 210 a couple of years ago, for $99, from PlanetGPS. Since the changeover to "Northstar", I understand prices have gone up.
If you don't mind 3 minutes with a calculator, it's great.

But if you're willing to pay an additional $250 to have the machine do the calculations, AND you don't mind having to have a square box, instead of a neat 2 1/8" flush mount in your console of dash, go ahead and get the 310.

[76Red18]

I figured the optimal throttle setting would constanty change due to load,wind,current,etc..After more digging ,I have found a 310 for $238. Mind posting the formula for the calcs.? Thanks for your input

[JohnB]

Take your speed, eg 30 mph, and divide it by your gph burn number, eg 10 gph, 30/10 = 3mpg. After a while, you just look at the gps for speed, and at the gph, and do the math in your head to come up with the most econmical milage.

Almost all 2 stroke motors get their best milage in the 3800-4200 range, so you select a prop, set the trim and tabs, move the coolers and occupants to get the best speed at that rpm.

Usually in doing this, you give up 1-3 mph on the top end, especially in the prop selection, but a boat is nothing but a floating compromise . I went with a 4 blade powertec that gives me 27 mph at 3900 rpm burning 12.6 gph for about 2mpg, but lost 2mph on the wot speed.

[76Red18]

Thanks John, Didn't seem like it would be that easy.

[cSickNick]

I went cheap, and bought a Navman 210 a couple of years ago, for $99, from PlanetGPS. Since the changeover to "Northstar", I understand prices have gone up.
If you don't mind 3 minutes with a calculator, it's great.

But if you're willing to pay an additional $250 to have the machine do the calculations, AND you don't mind having to have a square box, instead of a neat 2 1/8" flush mount in your console of dash, go ahead and get the 310.

Hi Frank,

keep in mind that this Lowrance unit will fit in the 2 1/8" hole and give you the display for MPG for $125 at BOE;

http://www.byownerelectronics.com/st...at=2996&page=1

Just wonder how good they are?

Since my Navman 210 crapped out, been looking to get MPG & GPH in the same dash hole.

Need to do some research on this, here is a start;

http://www.thehulltruth.com/forums/t...mode=1#M989112

[Bushwacker]

[/QUOTE]keep in mind that this Lowrance unit will fit in the 2 1/8" hole and give you the display for MPG for $125 at BOE;
http://www.byownerelectronics.com/st...at=2996&page=1

Just wonder how good they are?

Since my Navman 210 crapped out, been looking to get MPG & GPH in the same dash hole.


[/QUOTE]

The Lowrance unit is the same thing that BRP offers as one of their I-Command Digital gages. If you're running an E-TEC, it's an easy plug-in, just 1 cable to the EMM, and then all sensors and gages just hook in to network cable with T-connectors; gets fuel flow from engine computer. Needs speed input from NMEA compatible GPS antenna or paddlewheel sensor. They also mention Suzuki's on Lowrance Installation guide which you can download, so should be compatible with those motors. Not sure it will work with other motors - you'd have to ask Lowrance; they do have a separate fuel flow sensor you can buy.

I have the I-Command set-up and it's pretty neat for setting optimum trim. I can usually improve mileage by about .5 MPG by tweaking throttle, power trim and trim tabs. My E-TEC seems to be most efficient at about 2700-3000 rpm, around 25 mph and 5-5.5 gph; still over 4 mpg all the way up to about 4000 rpm however. (It interesting that this is about the same optimum cruise speed/mpg that Boating magazine got on a 140 I/O Seafari test back in 1969! Running angle went from 3.5deg/10mph to 2.5deg/20mph to ~1 deg @ 25+mph, so I've concluded that 20-25 mph speed range probably gives least wetted surface/drag and is therefore the most efficient speed for the 20' hull.)

Another and possibly cheaper option, if you just want to know fuel flow rate and gallons used, is Floscan. They've been making fuel flow meters for over 30 years - good aerospace quality stuff. I installed one years ago when running an old carbed 115 V-4; at 23-25 mph it burned 8-10 gph! At idle it burned 2 gph - I-Command says the E-Tec burns 0.2 gph at idle! Needle on Floscan meter doesn't even come off the peg at idle - have to goose the throttle to even tell if it's working!