Mercury SC1000 Gauges Do Wrong Fuel Management!

We continue to find out how accurately the SC1000 calculates fuel consumption.
0:00 Your outboard may not have a "how much is left" feature.
** FIRST TANK IS 25 LITERS, 23 LITERS FILLED. **
10:08 At 23l we see a full tank at 5 degrees, parking on the shore. At 3800 rpm and a speed of about 33 km/h we see a consumption of 9.6 l/h. When there should have been half a tank left (i.e. 10.5 l used) we do not see half a tank on the indicator, we drove 30.3 km, while the speedometer showed 10.1, a difference of 0.4 l. Speed ​​30.3 km/h, 5 degrees, consumption 8.9 l/h, 14.5 l used - still half a tank is NOT VISIBLE on the indicator. A little later after consuming 16.6 we see ALMOST half a tank, the speed is the same, the speedometer shows a consumption of 3.5 km/l. The beginning of the next day, consumption is 18.7l, i.e. there should be 4.3l left, but the indicator shows a lot. IT IS ALREADY CLEAR THAT EVERYTHING IS REALLY BAD. On the third day, in the morning, we check 19.5 liters of consumption, but we had 23 liters, and there is still almost half a tank left.
18:38 We consumed all 23l according to the SC1000 tachometer, but this is a lie. The discrepancy with the speedometer is already 0.8l. Pitch is 3 degrees. Well, and then we go very far beyond the 23l that we had. Stable zero on the indicator when 28.2l have been consumed. But if you lift the tank, you can see first segment, i.e. there are at least 4l in the tank, but I think there are about 6l (later it turns out that I was right). At 30.1l, when lifting the tank, we still see the first segment, i.e. there are at least 4l. At 32.3l, lifting the tank does not change anything on the indicator, i.e. we have less than 4l.
25:56 I even managed to finish fishing, the tank was almost empty. My calculation was correct. 35.1 liters out of 23 liters were used. I drove 96.3 km.
** SECOND TANK FOR 12 LITERS, 12 LITERS FILLED. **
26:44 Second tank installed. Fast driving starts at about 21h40m. At 21h52m the speed is 33 km/h, pitch is 4 degree according to the indicator a quarter of the tank has been consumed, according to the SC1000. A little more than half a tank on the indicator shows at 22h01m, when 5.4 l were used,. We drove for about half an hour.
30:44 As a result, by the beginning of the next day, the consumption was 6 liters - exactly half a tank, for half an hour of driving at a speed of about 33 km/h, now we will drive the same distance. THE SPEEDOMETER AGAIN SHOWS A DIFFERENCE - this time 0.2 l. Returned to the same place at a speed of about 24 km/h, pitch 6 degrees, consumption 13 l, indicator at zero.
33:33 We switch to the third one, recording 13.3 l consumption. We drove 27.7 km. On the trip calculator we see half of this - 14.3 km, because we reset it to the beginning of the day. And we drove slower in this direction (on average 21 km / h) and therefore 41 minutes, not half an hour. The remaining fuel is about 2.7 l. So in reality we used 9.3 l (approximately 1 hour 10 minutes of driving), i.e. DIFFERENCE 4 LITERS ON THIS SMALL TANK!
**THE THIRD TANK IS 25 LITERS, 23 LITERS HAVE BEEN FILLED. **
35:30 We reset everything and run from thunderstorms. 11.5 was used, the indicator showed a little more than half a tank. In reality, the indicator showed a half tank at a consumption of 13 liters on the SC1000. In general, everything is wrong.
39:40 I won't finish testing the last one, everything is clear anyway.
ANALYSIS OF THE TIME BETWEEN MEASUREMENTS GIVES THE IMPRESSION THAT THE CURRENT CONSUMPTION SHOWS CORRECT, BUT ONLY USED IS WRONG, but I'm too lazy to analyze. If someone is very observant, you can think about it and let me know in the comments.

[@fishelectronics]

ANALYSIS OF THE TIME BETWEEN MEASUREMENTS GIVES THE IMPRESSION THAT THE CURRENT CONSUMPTION SHOWS CORRECT, BUT ONLY USED IS WRONG, but I'm too lazy to analyze. If someone is very observant, you can think about it and let me know in the comments.