Fuel gauge not reading correctly

[kmcampbe]

I have a 01 Maxum 2100SR and I don't think that the fuel gauge is reading correctly. After being out on the lake most of the day yesterday it has not left the full mark and was still showing full when we got off the water. Tonight I'm going to pop the hatch and take a look at the tank level to see where it is. My question is how do I go about testing the fuel sending unit to see if it is functioning properly?

Thanks,

Kelly

 

[Silvertip]

Re: Fuel gauge not reading correctly

You test a sender by measuring its resistance. You can do this at two places. 1) If there is a hatch cover over the sender, disconnect the pink wire and measure resistance from the sender to ground. If you have a rough idea how much fuel is in the tank, the resistance should be 33 ohms full, 109 ohms 1/2 full, and 240 ohms empty. 2) If you don't have access to the sender, the pink wire on the fuel gauge "S" terminal is the other end of the sender wire. Remove it and measure resistance from the pink wire to ground. Same numbers apply. Be aware that fuel gauges are notoriously inaccurate and should be used as a reference. They will read very differently sitting at the dock than they will on the trailer and different still when underway. It all has to do with the attitude of the boat at the time you look at the gauge.

 

[UncleWillie]

Re: Fuel gauge not reading correctly

Keep in mind that the fuel sender is a linear device. It reads Half when the float is half way down.
If your tank is set on the keel it is likely "V" shaped. Half way down leaves 1/4 full, not 1/2 full, but it reads 1/2 full.
Your tank may read full for a long time and then go from full to empty in short order. Not unusual!
If you are sitting bow up and the fuel sender is in the rear of the tank, the issue is even worse.

Boat fuel gages are notoriously inaccurate. Not because if the equipment, but because of the circumstances of their use.
Before you go disassembling or replacing anything.... With the boat on the trailer, crank the bow DOWN, If the gauge now read more like you think it should, there is not much you can do to correct the issue.

A full day on the lake means a lot of different things.
5 hours of constant cruising at 3000 rpm is a lot different from hanging out on a sand bar.

How big is the fuel tank and how much fuel does it take to fill it back up.
That is the real measure of how full you are!