Fuel gauge trust

[scottinsydney]

1984 61MY

The fuel gauges on my boat are dead accurate so far, but the water tank sender in the master cabin floor tank is stuck.

My understanding is that there are two co-joined water tanks. The second tank is behind the beadhead along the inside transom.

1. If water tanks are full, then a lot of water would be spilt when removing the floor gauge and sender to check???

2. If the gauge was working it would only read the value in the floor tank anyway. ie. only when the floor tank was being consumed would the gauge move???

[PJ61]

TANK you to all who responded to this thread. I appreciate all the valuable knowledge that is shared thru out these pages. PJ61

[Glory]

Fill them and never run below 1/2. Those gauges are as accurate as a congressman's tax return.

If you have flowscans use them too.

At hull speed that might be ok, at planning speed you will have a 3,000 #s of dead fuel on board all of the time, 550 gallons weighing 3,900 #s. There is a fuel cost to transporting the extra weight.

If I had no confidence in my fuel gauge I would verify or fix it.

[Boatsb]

Remember my gauges read 1/2 at true 1/4 tank. I keep that as planned reserve so it's not a lot of extra weight.

Many of our tanks just don't have a consistent shape.

[Freeebird]

Remember my gauges read 1/2 at true 1/4 tank. I keep that as planned reserve so it's not a lot of extra weight.

Many of our tanks just don't have a consistent shape.

So, you're trusting inaccurate gauges to remain accurate with those inaccurate readings?

[Boatsb]

Fill before leaving for anything above 20 miles.

[racclarkson@gmail.com]

So, you're trusting inaccurate gauges to remain accurate with those inaccurate readings?

I have 910 gallons aft and 375 gallons fwd. Since my boat runs most efficiently with weight forward, I save the fwd as my reserve and don't invade it until below 1/2 of aft tank. At that point I will pull from fwd and return it aft down to 1/4 knowing I can't overfill and turning over the fuel in the fwd reserve tank. The fwd tank gauge is conveniently right on the mark all the way to the bottom. It helps that I've got clean fuel.

Keeping a graduated rod on top of the main tank, I've checked at different attitudes. Mine, like Scott's, is pretty much done at 1/4 on plane while I can still run (once anyway) slow on about 1/8 registering. I think it's a good idea to rod the tanks periodically just to stay ahead of an embarrassing moment. I think the 10% figure for usable fuel that Hat put forth is flirting with disaster.

[Freeebird]

Fill before leaving for anything above 20 miles.

Seriously?

Again, why drag around all that weight unless you anticipate running long enough to run 80% of it out?

Seems to me it would either be easier to replace/repair the gauge or just keep a fuel log once you figure your burn rates. An innacurate gauge is pretty much useless, IMO. My point was, how can you depend on your inaccurate gauge to give you ANY indication of your true fuel level? It could get either more optimistic or pessimistic without notice.

[Bob Bradley]

My tank gauge would read dead empty and still have at least a quarter tank left. I removed my vertical mount tank gauge and noted that it was 18". When I put a yardstick to the bottom, I discovered that the tank was actually 19-1/2" deep. Lo and behold, McMaster Carr carries a 19-1/2" gauge for $75. Problem solved. From observation, I find them quite accurate and slightly conservative (i.e. I usually have slightly more than the gauge reads).

Here: https://www.mcmaster.com/#float-gauges/=1c1ewkn

BTW, I heard a rumor that Floscan is going out of business.

[GJH]

The PO had cleaned and serviced my on-tank gauges shortly be fore I bought the boat, in tandem with installing remote tank-tender type gauges.
The ones on the tanks were spot on.
Perhaps the remote ones (which functioned like, but did not appear to be Harts) maybe were never calibrated correctly but read low on one (that's Ok IMO) and high on the other (not OK) each by about 1/8th.