Fuel Gauges

Looking for insight on fuel gauges. Our new to me 78 Marine Trader 34 had fuel tanks replaced in 2005. For some reason ther are no fuel gauges. I see the sender units in the tanks, but no wiring other than a ground.

Questions:
1. Do I need gauges made for the specific sender?
2. Have others used a dip stick Method? (I have my pilots license and we always dip tanks anyway, don't trust gauges)


Ray G

If you already have the hole in the tank, a Tank Tender system would be easiest to install.

No electric worries , but more bucks than a dip stick.

We se a Flo Master to keep track of fuel burn and only use the dip stick to keep the fuel dock honest.

Most elect fuel senders work by electrical resistance, so as long as the voltage is correctly matched should work.

Fuel gauges can be notoriously inaccurate. Adjusting the length of the float wire or bending it will change the reading and it's really just a guess as to how to accurately adjust/bend it. Furthermore the accuracy at different levels will change.

Best to dip stick it as this is the only real accurate method, or install a sight gauge. Most folks don't want to remove the sending unit to stick the tank or install a sight gauge so keeping track of fuel usage is an acceptable method of fuel remaining and probably more accurate than your gauge. Another method of course is to install fuel flow indicators which is an accurate method of determining fuel remaining as long as you fill your tanks at each re-fueling. But this will cost you a couple of boat $'s.

Keeping tack of your fuel usage by engine hours or mileage takes some time to accurately determine. But after a few tank fills you should get a pretty accurate determination of your fuel usage and hence the fuel remaining in your tanks.

My swing arm fuel gage is dead accurate as was the one on my previous boat.

raymond.goff said:

Looking for insight on fuel gauges. Our new to me 78 Marine Trader 34 had fuel tanks replaced in 2005. For some reason ther are no fuel gauges. I see the sender units in the tanks, but no wiring other than a ground.

Questions:
1. Do I need gauges made for the specific sender?
2. Have others used a dip stick Method? (I have my pilots license and we always dip tanks anyway, don't trust gauges)


Ray G

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If there are no gauges and no holes where gauges should be and if you can use a dipstick and are comfortable with using a dip stick, you might as well continue using the dipstick.

Gauges are convenient but as someone else pointed out they are normally not very accurate. Certainly not as accurate as a dipstick or sight tube. On my boat, filling the tanks to the top brings the marks well past the "F" mark on my gauges. I haven't experimented with the "E" mark, running out of fuel on a diesel boat is something best avoided. I usually refuel when the tanks are down to one third, just to be safe. With a dipstick or sight gauge I could do better.

In practice, I use the number of hours run from the last fill up as an indication of when to stop for fuel again.

You can usually mix and match senders and gauges. 30 to 240 ohms is almost an industry standard. You can measure the resistance range of your sender with a Vom meter then buy a matching gauge.

WesK said:

If there are no gauges and no holes where gauges should be and if you can use a dipstick and are comfortable with using a dip stick, you might as well continue using the dipstick.

Gauges are convenient but as someone else pointed out they are normally not very accurate. Certainly not as accurate as a dipstick or sight tube. On my boat, filling the tanks to the top brings the marks well past the "F" mark on my gauges. I haven't experimented with the "E" mark, running out of fuel on a diesel boat is something best avoided. I usually refuel when the tanks are down to one third, just to be safe. With a dipstick or sight gauge I could do better.

In practice, I use the number of hours run from the last fill up as an indication of when to stop for fuel again.

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Word of caution (re bold sentence above)... Only time I ever ran out of fuel on a boat was due to fuel gauge on single 150 gal tank that had always previously read very close to correct. That time it fooled me at reading near 1/2 full. Luckily we were in final leg (3/4 mile +/-) of a channel heading to our marina berth when both engines died; dropped anchor. Friendly fellow passing by did side tie and in the slip we were soon placed. I've never watched electric fuel gauges again... except for amusement. Stick method for me! That is 100% accurate with no chance of sight tube or other apparatus failure/leakage!

FF said:

If you already have the hole in the tank, a Tank Tender system would be easiest to install.

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I agree! I don't have the panel mounted fuel gauges like most have, rather, I have Tank tenders that are extremely accurate and are confirmed by an occasional sojourn to the lazarette where the tank sight glasses reside. Easier than a "dip stick" and just as accurate. Also, no electric is required.

Float gauges are very repeatable so if you record the readings as you fill the tank you can calibrate the gauge reading.


gauges will have specs as to the resistance reading for zero and full scale that must match the sender.

I installed a Cruz Pro fuel gauge. You start with a near empty tank for calibration. I'm accurate to a 1/10 of a gallon. Been using it for 10 years. Made in New Zealand I believe.

This would require some electronics but is an interesting solution: https://www.adafruit.com/products/1786

Sight tubes are probably near fool proof but requires one to go into the engine room/compartment. TankTender works well for me, which is visible in the pilothouse.

Art said:

Word of caution (re bold sentence above)... Only time I ever ran out of fuel on a boat was due to fuel gauge on single 150 gal tank that had always previously read very close to correct. That time it fooled me at reading near 1/2 full. Luckily we were in final leg (3/4 mile +/-) of a channel heading to our marina berth when both engines died; dropped anchor. Friendly fellow passing by did side tie and in the slip we were soon placed. I've never watched electric fuel gauges again... except for amusement. Stick method for me! That is 100% accurate with no chance of sight tube or other apparatus failure/leakage!

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I would love to be able to use the stick method but there is an "S" curve between the fill and the tank.

Maybe I could find a flexible stick.


As I understand it, running out of fuel in a diesel can be a big PITA.

Greetings,
"S" curve? No problem...

WesK said:

I would love to be able to use the stick method but there is an "S" curve between the fill and the tank.

Maybe I could find a flexible stick.


As I understand it, running out of fuel in a diesel can be a big PITA.

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We've "S" too, both tanks. 5 oz led torpedo sinker tied to thin tan fabric line... S curves no prob! Fill level easily distinguished. You know when sinker touches bottom by sound and feel. Calc what gallons per tank per inch. Simple math provides fuel amount remaining.

RT's solution reminded me of the tank level sounding tool I used in the Navy. They where brass sections with flexible riveted joints. The brass sections can be any length that would take the S bends of your fill fitting. Sort of looked like the old folding rulers carpenters used. Might be easy to fabricate if you can find some flat brass stock. The ones we used where drilled to hold liquid and the sections where 1 foot long to give us feet and inches with rounded corners to make the bends snag free and the riveted joints where loose so they would conform to the sounding tubes shape.
See technicalshipssupply.com "sounding rod" for ideas.

Art said:

We've "S" too, both tanks. 5 oz led torpedo sinker tied to thin tan fabric line... S curves no prob! Fill level easily distinguished. You know when sinker touches bottom by sound and feel. Calc what gallons per tank per inch. Simple math provides fuel amount remaining.

Click to expand...

That might work for me. I would put something on the other end of the string so it can't be dropped into the tank.

Rather than math, I'm thinking a chart would be easier. Do the math just once.

WesK said:

That might work for me. I would put something on the other end of the string so it can't be dropped into the tank.

Rather than math, I'm thinking a chart would be easier. Do the math just once.

Click to expand...

So not lost in tank: I have the line long enough so that end-loop fits snug over wrist... with several feet not needed down the filler tube before sinker hits tank bottom.

My tanks hold just over 4 gal per inch. I have the 1/2 full level marked on the thin line. In seconds I can closely estimate number of gallons in tank.

Storage is a snap... <4 cubic inches in a cubby hole.

Happy New Year... Everyone! - Art

I suppose I would need one for each tank as a string couldn't be wiped clean like a real dipstick. No problem, this sounds pretty inexpensive.

WesK said:

I would love to be able to use the stick method but there is an "S" curve between the fill and the tank.

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I have the same problem, sharp curves in the fill hose to the tank.

Here's what I use:



I did scuff it up a little with a wire brush to make the wet line more visible. Early on I lost the tip, fortunately NOT into to the tank, so I'd recommend just taking it off before using.

I've also used it to help fish some wires through the boat.

CaptTom said:

I have the same problem, sharp curves in the fill hose to the tank.

Here's what I use:

I did scuff it up a little with a wire brush to make the wet line more visible. Early on I lost the tip, fortunately NOT into to the tank, so I'd recommend just taking it off before using.

I've also used it to help fish some wires through the boat.

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I thought of that myself a few minutes ago. I use to use these at work often and of course I have one for work around the house and around the boat.

I think I would just cut off enough to stick the tank, not carry the whole thing around.

It would be important to bend the tip back and secure it so it doesn't get stuck in or damage the rubber hose. You have to heat the metal to bend it without breaking it. Many of these come with a loop already at the end. Yours must have had an attachment of some sort or you wouldn't have lost it.

In the picture, you can see the plastic tip that eventually came off. True, what's left behind is a metal edge, but I don't think it's sharp enough to hurt the hose. My concern would be having it come off inside the tank when it's pulled back out. But filing down the edge wouldn't be a bad thing.

I leave it on the spool. It's made of something like spring steel, and it's an unmanageable mess outside the spool. Once reeled back in, I can toss the whole thing in the junk drawer.

From deck fitting to bottom of the tank, I need a little over 4 feet. The tanks themselves are 28" high, so I filed 30 marks, one per inch up from the bottom.

The PO used a length of 12-3 Romex wire to stick the tanks. He had a piece of electrical tape at the bottom, one to mark the top of the tank and one in the middle. I tried it for a while but it was really hard to see the wet/dry line. But it worked for him so I offer it here as another simple solution. Easy to coil up and stow, easy to uncoil.

If gravity will work well enough....these are or similar the tapes with a weight on it that the old USCG cutters used to use to measure their tanks onn some of the bigger cutters.

Some were metal and some fiberglass tape. Sometimes known as a surveyors tape. May be easier than the more rigid fish tape.

Do you guys who use dip sticks to gauge your tanks know about water finding paste?
It comes in a tube like tooth paste, you smear some on the dip stick and if there is water in the tank it changes color. You can tell how deep the water is in the tank bottom.

CaptTom said:

In the picture, you can see the plastic tip that eventually came off. True, what's left behind is a metal edge, but I don't think it's sharp enough to hurt the hose. My concern would be having it come off inside the tank when it's pulled back out. But filing down the edge wouldn't be a bad thing.

I leave it on the spool. It's made of something like spring steel, and it's an unmanageable mess outside the spool. Once reeled back in, I can toss the whole thing in the junk drawer..

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It is spring steel, that's why you have to heat the end if you want to make a loop. Like I said, I used these and bigger ones frequently for over twenty years.

You can get fiberglass ones now (much safer for fishing around live circuits).

Four or five feet cut off wouldn't be a problem to store but if you're happy with the whole thing, that's fine. My boat is probably much smaller than yours.

Our large snakes were kept in check by coiling them through a short section of flexible metallic conduit and taping the ends.

HopCar said:

Do you guys who use dip sticks to gauge your tanks know about water finding paste?
It comes in a tube like tooth paste, you smear some on the dip stick and if there is water in the tank it changes color. You can tell how deep the water is in the tank bottom.

Click to expand...

That sounds like a great idea.

You fellows using various tapes to sound your tanks might want to put a grounding wire on them. All of the commercially made ones have grounding wires. I guess they could build up static electricity and make a spark. Probably not a significant issue on diesel tanks. This link will take you to a picture of a commercially made sounding tape.
http://www.bettymills.com/shop/prod...S700-58814 - U.S. Tape Oil Tank Gauging Tapes

HopCar said:

Do you guys who use dip sticks to gauge your tanks know about water finding paste?
It comes in a tube like tooth paste, you smear some on the dip stick and if there is water in the tank it changes color. You can tell how deep the water is in the tank bottom.

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Ok, Parks... What's the paste's name? You sell it? H N Yr & Cheers!! Art

Hi Art, The brand I sell is called Kolor Kut. I think there are several brands on the market. Try to find it locally. If I ship it to you, the shipping charges would be as much as the product. If you can't find it near you, I'll be glad to mail it to you.

The color change is very dramatic. It goes from baby crap brown to vivid red when it hits water.

HopCar said:

Hi Art, The brand I sell is called Kolor Kut. I think there are several brands on the market. Try to find it locally. If I ship it to you, the shipping charges would be as much as the product. If you can't find it near you, I'll be glad to mail it to you.

The color change is very dramatic. It goes from baby crap brown to vivid red when it hits water.

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TY, Parks!