Fuel Gauge/Sender Questions

[Philster]

Parked on the trailer, with a full tank, my fuel gauge will read 3/4 full and rapidly spike up to full and back to 3/4.

It's one of the pesky things I just need to obsess about. I am guessing there is an opportunity for this to work better. In such a case, does this sound like a sending unit issue?

How would I check/fix/etc.

I have run outboards w/portable tanks and had a Baja that had a fuel gauge that never worked (and I didn't care because I was a punk kid).

Well, now I want this one to work. What steps would I take to make sure it's as accurate as possible?

 

[Silvertip]

Re: Fuel Gauge/Sender Questions

Understand that fuel gauges are "fuel level" gauges -- not "fuel quantity" or "fuel gallons" gauges for the simple reason they operate via a float on the end of a movable arm. With the boat on a trailer the fuel level in the tank is at a different orientation than it is with the boat in the water. In fact the gauge may read differently under way than at rest. So pick one orientation to read the gauge and be happy. You know when the tank is full because you filled the tank and it spit back at you -- correct? So you want the gauge to be accurate at empty. Many folks think that when the gauge reads 1/2 they have 1/2 the amount of fuel remaining when in fact that is true ONLY if the tank is of uniform shape and the tank is perfectly level. Case in point! Take a cone shaped container, like an ice cream cone or paper cup. When full, an 8 ounce tapered container contains 8 ounces. When half full however, there is less than 4 ounces in the cup because the bottom 1/2 of the container is smaller (by volume) than the top half. So applying the float principle, there is no way the gauge can register the actual contents in gallons or quantity. It can only register level. Whew!!!!!!! Now back to your question about how to fix it. Do you want the gauge to register accurately at empty, 1/2, or full? You likely can't have it all three ways. To adjust it you move the float on the arm to change the rate of swing on the arm, or you bend the arm. In your exact case, IF and I repeat IF the float is not fuel soaked so it is partially sinking, then you would move the float closer toward the sender to make the gauge read full. But realize the sender may reach its travel limit before the float actually touches the bottom of the tank so now you've made the gauge inaccurate on the EMPTY side. See how this works? It may be the sender may not be the correct depth for the tank as well. Lots of variables and no cut and dry solutions to making a gas gauge accurate across the entire range.

 

[H20Rat]

Re: Fuel Gauge/Sender Questions

the ONLY way you are going to get a 100% accurate fuel level reading on a boat is with a fuel flow meter w/memory. Zero it out when you fill, and then it will keep track of how many gallons you have burnt. I know at least some of them also have a programmed option where you tell it your tank capacity and it subtracts for you, telling you the remaining fuel.

 

[Philster]

Re: Fuel Gauge/Sender Questions

Since I am obsessive, the meter is the ticket for me. Anyone set one up and have "do's and don'ts" to suggest? I suspect they need calibrating.

Any advice? Recommendations? I see the Lowrance with sensor is around 200 US dollars.

 

[Silvertip]

Re: Fuel Gauge/Sender Questions

I have this one. It uses a turbine style transducer in the fuel line. It MUST NOT be allowed to vibrate so rubber mounting is necessary and the transducer must not be mounted sideways. Otherwise pretty straight forward installation. works great. Provides instantaneous and average fuel flow in gallons or liters/hour, fuel remaining, total fuel burned or per trip. That manufacturer was sold to Northstar.

 

[H20Rat]

Re: Fuel Gauge/Sender Questions

i'm so torn about fuel flow gauges... i've had them in an online shopping cart more than once, and then back out... the other part of me doesn't WANT to actually know what how much i'm burning, its a hobby and for entertainment, never keep track of the costs of hobbies unless you are trying to find a new hobby.

 

[Philster]

Re: Fuel Gauge/Sender Questions

Well, when you run up the east coast in the Atlantic, or run for hours through the intercoastal waterways which run from FLA to New England, and make crossings of the Delaware Bay and Chesapeake Bay from one state to another and explore their bays, waterways and sounds, ya gotta keep a serious on on fuel and know where you can refuel.

My cruise speed is 42-45 MPH, and the gauge is gonna read something like, "Now Burning Money Rapidly".... but it still costs them same when I get to the pump.

Actually, if you have the meter setup right, I would imagine it could help you pick the right cruise speeds and adjust for max economy accordingly (based on all the reading I've done today looking for a fuel flow meter!).

 

[Silvertip]

Re: Fuel Gauge/Sender Questions

Fuel flow monitoring isn't just about cost -- it is about instantly knowing if you have an engine problem or not. A 75 HP engine (like the one this unit is monitoring) shows the engine burns exactly 7.5 gallons/hour at WOT. If that flow rate suddenly went to 8 or more under the same operating conditions and load, there is an issue and you know that before you are the length of a football field from the dock. It is also about safety in that you know precisely how much fuel you have left and based on the flow rate you know how long you can run before reaching for the paddles. It's a tool, not a toy.