Fuel gauge sending unit

A/C & D/C Wiring, GPS, Radios, etc.
Louky
Tin star
Posts: 21
Joined: Mon Jul 14, 2014 8:38 am

Fuel gauge sending unit

Post by Louky »

One of my fuel gauges reads 1/4 when its full and the other one doesn't read at all. Someone suggested that i need to replace the tank sending units. He said I need to measure the dimensions of the tank and get the appropriate size.

Can you guys offer any advise on the procedure, things to check 1st, or best brand units to purchase?

Thanks
Louky
1987, 32' Marinette Fisherman
Col. Angus
Louisville, KY
Twin Chysler 360's
Supersport18
Tin star
Posts: 83
Joined: Wed Jul 16, 2014 3:52 am

Re: Fuel gauge sending unit

Post by Supersport18 »

Verify 12v to gauge. verify meter function by grounding wire to sending unit while assistant observes fuel meter for full deflection. Next check resistance of sending units and also check connection to ground from sending unit on tank. Clean all connections. Cleaning connections will solve problems 90% of the time.
1986 Sedan Flybridge
Twin 318 closed loop
" Little Martha"
Traverse City,Mi
Hydraulic Steering (both helms)
Autopilot (both helms)
Supersport18
Tin star
Posts: 83
Joined: Wed Jul 16, 2014 3:52 am

Re: Fuel gauge sending unit

Post by Supersport18 »

heres a basic wiring schematic.
Attachments
1105a.jpg
1105a.jpg (28.41 KiB) Viewed 13570 times
1986 Sedan Flybridge
Twin 318 closed loop
" Little Martha"
Traverse City,Mi
Hydraulic Steering (both helms)
Autopilot (both helms)
yooper
Aluminum Star
Posts: 123
Joined: Mon Jul 14, 2014 10:24 am

Re: Fuel gauge sending unit

Post by yooper »

Your 1986 will take a standard 5 hole mounting plate. I just looked around the web. It looks like Moeller brand is one of the last left standing. Jamestown Distributors has very thorough step by step instructions on installation. There are two basic types types of senders. The most common uses a float on the end of a swing arm attached to a rheostat. The measured resistance shows on the dial and will vary based on the level of liquid in the tank. This system is inherently inaccurate because the liquid in a boat tank sloshes around a lot as the boat moves. The big point of failure is when the pickup wears and no longer wipes the coils in the rheostat. As the unit wears the arm starts moving side to side as well as up and down. 'The new Moellers look better that the ones I put in and they claim that they are all stainless steel. The second type offered is a "reed type" where the float moves up and down on a stationary pipe. This looks like a better design but I have no personal experience with it. When you install a swing arm it must be long enough to cover the depth of the tank and stay clear of the tank sides and any baffles. My old ones were sized and oriented correctly so I just copied the set up over to the new units. I had a heck of a time installing the port side sender. It was deep under the cockpit deck. I lost a couple of tools and some screws and washers under the port side fuel tank. That stuff is still there. It is now officially ballast. If that sender ever goes out again I am cutting a 6" inspection port in the deck right over the sender.
Louky
Tin star
Posts: 21
Joined: Mon Jul 14, 2014 8:38 am

Re: Fuel gauge sending unit

Post by Louky »

Thanks supersport18 for the testing procedure and schematic, I'll definitely check that out first and hopefully I'll be one of the 90%. Yooper, your research was a big help. I hope I don't have to replace the sender, but if so, I'll check with Jamestown Distributors first.

Thanks again,
Louky
1987, 32' Marinette Fisherman
Col. Angus
Louisville, KY
Twin Chysler 360's
Dougrose
Member
Posts: 16
Joined: Sun Jul 13, 2014 7:04 am
Location: Germantown, Maryland and Merritt Island, Florida

Re: Fuel gauge sending unit

Post by Dougrose »

I use electronic senders from http://centroidproducts.com/ that are made with a wire inside a tube. The electronics measures the capacitance between wire and tube and figures out how much of it has fuel (or water) in it and drives the standard gauge. Have been using them for years, have bought at least a dozen, and none have failed.

Marinette senders are standard 240/33 Ohm with two wires: http://centroidproducts.com/nintro.htm
Doug Rose
32' Cabin Cruiser
Twin Perkins 120hp Diesels
Merritt Island, Florida
Fastjeff
Site Admin
Posts: 1521
Joined: Sat Jul 12, 2014 5:06 am
Location: Rock Halll, MD

Re: Fuel gauge sending unit

Post by Fastjeff »

It's a royal P in the A to do this, but both gages can be removed (easy if you're an orangutan) and adjusted via the 'wooden stick' method to read the way you want. On mine, when the gage is on 'E' I have roughly 12 gallons left in each tank. (I did the math to determine that: Dimensions of the tank and fuel level from the wooden stick.) And my brilliantly accurate calculations were confirmed the next time I filled up!

These settings are comforting when the gages get way down there and the nearest marina is a far piece away!

Jeff
"We live at the bottom of an ocean of air, not at the top." General Marvage Slatington
Supersport18
Tin star
Posts: 83
Joined: Wed Jul 16, 2014 3:52 am

Re: Fuel gauge sending unit

Post by Supersport18 »

Another consideration would be to install flow meters . Putting some on my 32 this year.
1986 Sedan Flybridge
Twin 318 closed loop
" Little Martha"
Traverse City,Mi
Hydraulic Steering (both helms)
Autopilot (both helms)
Fastjeff
Site Admin
Posts: 1521
Joined: Sat Jul 12, 2014 5:06 am
Location: Rock Halll, MD

Re: Fuel gauge sending unit

Post by Fastjeff »

The problem with relying on the flow meter to tell you how much gas has been consumed is someone (not you, of course!) may accidentally turn off the Perko switch and poof! your reading(s) are gone, off to electronic never-never land.

Jeff
"We live at the bottom of an ocean of air, not at the top." General Marvage Slatington
Supersport18
Tin star
Posts: 83
Joined: Wed Jul 16, 2014 3:52 am

Re: Fuel gauge sending unit

Post by Supersport18 »

Was not aware of that. Planning on using Lowrance meters.
1986 Sedan Flybridge
Twin 318 closed loop
" Little Martha"
Traverse City,Mi
Hydraulic Steering (both helms)
Autopilot (both helms)
Post Reply