Cruisers Forum
 


Join CruisersForum Today

Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 28-08-2018, 04:48   #1
Registered User

Join Date: Apr 2017
Location: Boston
Boat: Boston Whaler, Conquest 315, 31ft
Posts: 212
Fuel gauge wildly inaccurate, is that typical?

I have a Boston Whaler, a well-built boat, but the electronic fuel gauge is wildly inaccurate.

For example, the tank supposedly holds 291 gallons, but if I fill it up, it reads 262.

I can put 50 gallons in the tank and the gauge will not change. For example, the gauge reads 150. I add 50 gallons. The gauge does not change.

Yesterday, I had 100 gallons in the tank (according to the gauge). I added 100 gallons (metered). The gauge then read 162.

Is this typical for boats, or should I investigate removing the OEM (Boston Whaler) gauge and replacing it with something different?
__________________

jsc7 is offline   Reply With Quote
Old 28-08-2018, 05:30   #2
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Helsinki (Summer); Cruising the Baltic Sea this year!
Boat: Cutter-Rigged Moody 54
Posts: 24,846
Re: Fuel gauge wildly inaccurate, is that typical?

Typical for boats. Ordinary fuel gauges are not intended to give you an accurate to the gallon read of fuel state; just a general idea. Most people calibrate their gauges in their heads -- they know that fuel is actually down by 100 liters (or whatever) when the needle first moves off Full, and that you've still got 100 liters (or whatever) when the needle first touches red, and everything in between is a rough approximation.


If you want to know your fuel state with accuracy, then you really need to invest in flow meters, the way they do it on high end power boats. Know how much is in your tank, then set the flow counter to zero when you're full, and you will always know very precisely where you are.


And/or:


Buy a good fuel sensor and calibrate it. Maretron make an ultrasonic one which can be programmed and calibrated. Or there are pneumatic ones ("Tank Tender") which will tell you the static pressure at the bottom of the tank, and you read that against a calibration card which translates that into the quantity of fuel remaining.




All of this is quite a lot of expense -- do you really care? Most people just learn to interpret what their carpy original fuel gauge tells them, and learn the limitations of it.
__________________

__________________
"Parce que je suis heureux en mer, et peut-Ítre pour sauver mon ame. . . "
Dockhead is offline   Reply With Quote
Old 28-08-2018, 05:30   #3
Senior Cruiser
 
Sailmonkey's Avatar

Cruisers Forum Supporter

Join Date: Sep 2009
Location: Houston
Boat: '76 Allied Seawind II, 32'
Posts: 7,234
Re: Fuel gauge wildly inaccurate, is that typical?

Iíve never been on a boat with an accurate fuel gauge that wasnít a sight tube.
Sailmonkey is offline   Reply With Quote
Old 28-08-2018, 05:33   #4
Registered User

Join Date: Aug 2016
Location: East Cackalacky
Boat: Hunter 340, 1999, 34'
Posts: 182
Re: Fuel gauge wildly inaccurate, is that typical?

My fuel, water and holding tank gauges all are wildly inaccurate. Replacing them doesn't help. You learn to read levels by other signs.
Attikos is offline   Reply With Quote
Old 28-08-2018, 05:47   #5
Registered User
 
scotty c-m's Avatar

Join Date: Dec 2012
Location: Santa Cruz
Boat: catalina 400 MKII
Posts: 238
Re: Fuel gauge wildly inaccurate, is that typical?

I agree that fuel guages are often inaccurate. However, the gauge described by JSC7 sounds different. You should get some consistancy from your gauge, and that helps when using it. I would explore getting a more consistent gauge.
scotty c-m is offline   Reply With Quote
Old 28-08-2018, 06:04   #6
Registered User
 
Fence Man's Avatar

Join Date: Dec 2016
Boat: Stardust Cruisers HB 73'
Posts: 337
Re: Fuel gauge wildly inaccurate, is that typical?

Every boat I've owned showed empty on the gauge(analog) at right around half a tank. I don't know if there is a reason for that, or if I'm just lucky.
Fence Man is offline   Reply With Quote
Old 28-08-2018, 06:07   #7
Registered User

Join Date: Jun 2012
Location: Port Aransas, Texas
Boat: 2019 Seawind 1160 Lite, Previous 2002 Seawind 1000
Posts: 1,310
Re: Fuel gauge wildly inaccurate, is that typical?

I have a fishing boat with a very shallow but long and wide tank. Holds 60 gal fuel. Motor is 250 hp Yamaha SHO. Gauge very inaccurate so I hooked up the motor ECU to the NMEA network. Now my Garmin plotter gets instantaneous fuel consumption and integrates to show me "fuel remaining". Very accurate. When you add fuel you enter into Garmin and setting gallons added. Just as good as having accurate fuel remaining is having the instantaneous fuel consumption number. I think my motor burns 6-7 gal per hr at 25 mph and over 30 gal per hr at WOT of 50+ mph.
sailjumanji is offline   Reply With Quote
Old 28-08-2018, 07:29   #8
Registered User
 
ranger42c's Avatar

Join Date: Aug 2012
Location: Maryland, USA
Boat: 42' Sportfish
Posts: 3,939
Re: Fuel gauge wildly inaccurate, is that typical?

Some senders -- float arm senders -- can sometimes be slightly adjusted. Pull it out and yutz with it.

Sometimes associated gauges can be adjusted; check the manual.

Sometimes a "general idea" is about as good as a given sender/gauge pair will get, sometimes inhibited by sender and/or gauge, but also very dependent on tank shape versus sender type.

For example, the quantity of new fuel injected into a tank with a deep V at the bottom will have a different affect on sender float height (or change in height) than might that same quantity at the higher part of the tank.

And in the grand scheme of things, senders using resistance curves to inform gauges... aren't rocket science... and in turn they're just not as accurate as rocket science. Another example of that might be when the sender is near the aft section of the tank; often that means fuel height in the aft part of the tank will increase when you're underway; sender float rises, gauge displays more fuel than you had at rest.

-Chris
__________________
Selby Bay, South River, Chesapeake Bay, USA.
ranger42c is offline   Reply With Quote
Old 28-08-2018, 08:21   #9
Registered User
 
Chalifour's Avatar

Join Date: Oct 2014
Location: Marmaris Turkey
Boat: Jeanneau Sun Odyssey DS43
Posts: 120
Re: Fuel gauge wildly inaccurate, is that typical?

Best fuel gage you can get is you! Simply know how many liters your engine consumes per hour and than keep track of the engine hours from fill up to fill up.
Only requires that you fill up full every time.
Than you can sell your fuel gage !!!
Chalifour is offline   Reply With Quote
Old 28-08-2018, 08:27   #10
Moderator
 
Pete7's Avatar

Cruisers Forum Supporter

Join Date: Aug 2009
Location: Solent, England
Boat: Moody 31
Posts: 11,773
Images: 14
Re: Fuel gauge wildly inaccurate, is that typical?

I use a garden cane with marks for every 5 gallons.

However, as Dockhead said there are meters based on the flow rate of fuel to the engine. Reasonable prices for petrol engines.

Pete
Pete7 is offline   Reply With Quote
Old 28-08-2018, 08:46   #11
Registered User

Join Date: Aug 2011
Location: New York, New York
Boat: Dufour Safari 27'
Posts: 976
Re: Fuel gauge wildly inaccurate, is that typical?

Quote:
Originally Posted by Dockhead View Post
- do you really care? Most people just learn to interpret what their carpy original fuel gauge tells them, and learn the limitations of it.

Excellent point. None of my boats even have a fuel gauge. They have a stick that I dip into the tank so I can see roughly how much is left. I know how much the tank holds and I know my approximate fuel burn rate. Often I don't even use the stick. When I think I am getting low I may check with the stick or more often I just pump some fuel from the jerry can into the tank and use the stick to see how close to full I am getting.
ArmyDaveNY is offline   Reply With Quote
Old 28-08-2018, 09:05   #12
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 21,508
Re: Fuel gauge wildly inaccurate, is that typical?

It's typical for most boat gauges. The tanks are odd shaped or V shaped and it's not a linear measurement. Knowing your average usage per hour and logging that helps. Then adjust your gauge so it measures accurate-ish on the last half of the tank to know when you are getting low is about all you can do.
There may be new fangled programmable electronic types out there now...?

There are fuel flow meters that go in your fuel line available (like aircraft use).
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 28-08-2018, 10:06   #13
Registered User

Join Date: Jul 2017
Posts: 208
Re: Fuel gauge wildly inaccurate, is that typical?

I guess it depends on the boat.

On my boat, the fuel gauge always indicates full, no matter how much fuel is in the tank... (well, I only tested down to 1/4 of a tank, still "full"). I had a mechanic opening the tank and testing the gauge, and apparently it is working fine, it is likely the shape of the tank that makes it inaccurate.

Tank Tender or similar devices sound like an excellent idea. Expensive, but they are certainly at the top of my wish list for next season.
FabioC is offline   Reply With Quote
Old 28-08-2018, 10:44   #14
Registered User

Join Date: Aug 2018
Posts: 1
Re: Fuel gauge wildly inaccurate, is that typical?

I removed the fuel tank gauge and it appeared to be in good working condition. After testing the gauge with an ohm meter I found the rheostat worked nicely when the float was in the high tank level position but below half tank level the rheostat showed and open circuit. The rheostat was an open type so I scratched the corroded area with my pocket knife and retest. Now the gauge worked down to one quarter tank before showing and open circuit which was still not working good enough. Ebay sells the gauge assembly but I would like to get just a new rheostat.
winddrifter is offline   Reply With Quote
Old 28-08-2018, 11:49   #15
Marine Service Provider

Join Date: Sep 2011
Location: California
Boat: Alerion Express 38 Yawl (former)
Posts: 428
Re: Fuel gauge wildly inaccurate, is that typical?

Boat tanks are frequently wide, flat, and oddly tapered to fit compactly against the hull. Any motion of the boat tends to cause some sloshing, and boats that are not trimmed (or bow-high due to being on a plane) will show inaccurate readings. It's a tough challenge.

I have a few thoughts that might help, however.

1. Change to a fuel consumption meter so you can "zero" your tank when full and measure how much you consume.
2. Swap out your sensor for a better model. Not sure what you have now, but the lack of smooth increase/decrease means to me that you might benefit from a WEMA or similar sensor.
3. Some readouts calibrate the tank to peculiar, non-linear tank designs. Blue Sea Systems, for example, allows you to take an empty tank and fill it at a constant rate, which calibrates the tank despite odd shapes.

Cheers,

Chuck Hawley
__________________

Chuck Hawley is offline   Reply With Quote
Reply

Tags
cal, fuel

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Beneteau fuel gage wildly wrong davefromoregon Engines and Propulsion Systems 18 01-08-2017 04:45
Beneteau Oceanis 40 fuel gauge is inaccurate AFKASAP Monohull Sailboats 22 14-12-2015 11:06
Most inaccurate TITANIC doco' EVER! djaustralia Monohull Sailboats 24 29-03-2013 01:26
Inaccurate RYA Teaching : CTS - Quest For a New Method Seaworthy Lass Navigation 855 23-02-2013 17:58
Battery Monitor Inaccurate % when Using a Propshaft Alternator Fuss Electrical: Batteries, Generators & Solar 4 15-10-2009 15:45



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 20:10.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.