Garmin GFS on twins

[1st grady]

I purchased a used/never installed Garmin GFS fuel management system and intend to hook it up to my garmin 4000 series GPS. I have twin 150 HPDI motors. I was thinking of just installing the one sending unit for now in order to identify fuel consumption rates. Can I just double the flow (mentally) if I run two motors at identical RPM? I am just looking to run the motors more efficiently.

 

[Blackbird]

You'll probably be close but unless the engines are absolutely identical which is rare, they will probably burn fuel at slightly different rates, maybe as much as a 10% difference. I had a pair of the Yamaha 150's and according to the Yamaha instrumentation, they were never exactly the same, even though I had them serviced at the same time. They both put out full power but one always burned a little more. I now have a pair of 250 4-strokes and same thing. One consistantly shows a higher burn rate. Not a lot but enough so if I simply doubled one's rate, I would be off overall. Hope this helps.

 

[1st grady]

Thanks for the info. I am mainly looking for the optimum running RPM, which I would imagine is similar for both motors and a rough consumption total. I understand the data will not be precise. I will eventually connect a second meter. Right now I am estimating by the fuel gauge, probably not even close to actual.