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Whenever I can finally rip the shrinkwrap off my boat, I'm going to install a Navman 2100 fuel computer. Since I don't trust my fuel gauge (unreadable in any kind of sea and doesn't accurately reflect fuel capacity), I was just going to put the Navman in the same hole on the console that the gauge is currently in. A thread on another board seems to indicate that this is a bad idea (i.e. you should have both the computer and the gauge), but I can't figure out why. If you can't trust your fuel guage anyway, what's the problem with only going by the fuel computer?
Since my boat is in a slip, I generally keep it topped off since I don't like humping more 5 gal. cans than I have to. I won't be using the Navman to tell me when to fill up, but rather what my fuel level is when I'm out for the day.
Any reason my plan to only have a fuel flow computer in the console is a bad one?
i thought about it too, wound up keeping the gauge
couple of things:
-fuel needle however inaccurate is at least some backup
-the fuel gauge helps when you go to fill up so you can tell when you're full
-consider the 3100 if it's not too late...it has an interface for your gps to enable a display of mpg, estimated range remaining, and a trip computer
I had the same situation and opted to leave in the fuel guage. It never hurts to have a backup, and in the event I swap out my tank at some point, It will allow me to install a new guage. Personal choice really.
BTW I love the navman, just remember to reset it when you add fuel.
Any reason my plan to only have a fuel flow computer in the console is a bad one?
Nope. There is no reason not to do it. Wanting to keep a backup fuel gauge to get an unreliable fuel reading is a waste of console space. Pop out the old techology and put in the new. If you have a total electrical failure and can't read the Navman then you have bigger problems than knowing how much fuel you have in your tank IMHO.
My fuel guage is part of the speedo/ oil guage on my Yammy, so it had to stay.
What I did was put the flow meter in the hole where the hour meter was. Just strapped the hour meter under the dash, out of the way.
No need to be looking at it every trip .
Using a fuel flow gauge in place of a fuel quanity gauge is a terrible idea. If the fuel gauge is wrong, then fix it, don't put a band aid over the problem. There are fuel quanity indication systems available that do work, and work very well.
A fuel flow gauge can not tell you the quantity of fuel in the tank. All it can do is measure fuel consumed. Certainly some calculations can be done to try and determine the fuel remaining if the fuel you started with is known, but that is a bunch of mumbo jumbo and subject to errors.
Two things come to mind on this issue. On the recent around the world unrefueled flight by Steve Fossett the airplane lost some fuel due to fuel venting. However, they did not know what the problem was at the time. Based on the fuel flow system they knew what they were burning and had consumed (and could determine what SHOULD have remained by calculations) but based on the fuel quantity system they were told they had less fuel. They had to go with the fuel quantity indication system and rightly so.
There was an Air Transat Airbus flying from the US to Europe a year or so ago (maybe longer). A fuel line broke and they were dumping fuel but it was unknown to the flight crew. The break was upstream from the fuel flow transmitter. Anyway, when they got a low fuel light from the quantity indication system they thought, this can't be right. We are consuming X pounds per hour, we started with Y pounds and we have only been flying for several hours. We must have sufficient fuel to go on. And on they went. When both engines flamed out from a lack of fuel they were extremely lucky and were able to glide to Lajes in the Azores where they made a dead stick landing. I believe the flight crew was cited and faulted for failing to adequately monitor and use their fuel gauging system.
Put a fuel flow meter in. It is a good idea. But fix the fuel quantity system if is broken.
I redid my instrument panel, installed a 2100, and dropped the fuel gauge.* My boat has inspection plates above the fuel tank and there's a mechanical fuel gauge that's part of/attached to the sending unit.* I replaced the deck plate with the clear plastic, screw-in type and that's my "back-up" if the Navman fails.
If you have just a fuel gauge (and the overwhelming majority believe them to be very inaccurate), your current fuel level for every trip is half your own intuition (how much gas did I put in last time? how much have I run? etc.) and half going by the fuel gauge.* That's if the needle ever stops moving.* If you have a flow computer, you have much more accurate fuel consumption data, typically only off by less than a gallon from actual and when they're off, they usually are in the safer direction, meaning they tell you you've used more fuel than you really have used, leaving more in the tank.* Why have the fuel gauge as a back-up if it's inaccurate?* You'd have the same or better accuracy using your fuel receipts and the tripmeter on the GPS. Just my opinion.*
__________________ "One would think that the earth was the road Of the body, that the sea was the road Of the soul."
Navman 2100 as replacement for fuel gauge? 
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