Fuel Gauge Accuracy

0515 I woke remembering an issue years ago, I was called in rite before the boat was to sell.
Some previous tech (owner?) was using the tank bonding for a battery negative connect*.

I did find the original pink and black wires. The wire strands were black and near dissolving. Then poor crimps under the dash.
So much resistance, the fuel sender / gauge never had a chance.

Many hours later, new wires run, the old sender and gauge worked perfectly.

Could you have some extra resistance lurking in your wires?

* Against ABYC and many other common sense rules; Bonding is never used for any electrical device.

That guy Les who specializes in old Hatteras alarm circuit boards you had suggested weeks ago, who drove up from Miami for a day and found the alarm LED's issue commented how great all the Bertram wiring was so I doubt it. Also before installing the reed style KUS sender in the fwd. tank I also hooked it up to the gauge wires for the aft. tank as a test and the gauge needle moved E to F as the float was moved. Sucks their floats diameter is more then the aft. tank sender tube so probably order a new 28" Centroid 3 wire sender tomorrow as unable to find another one to fit the tube. In poking around another boat forum last night I ran across several posters who recommended them so given no other options as of yet, worth a try before marking a long 1/4" wood stick.

How small of a tube? Differance to float size?
You may want to call Wema/Kus and ask if a smaller float is available or another style of sender.

Glass tank? Removable hardware with out pulling the deck?
You may consider cutting that tube out and going with the Wema/Kus sender there also.


BTW,
Was working on a new (big & fancy) Contender last year. Wema/Kus senders installed, in alloy tanks.
The last 3-4 inches of the forward gas tank was blocked off and used for diesel fuel.
3 big Verados and a lil diesel gen-set.

If I recall, that third wire is battery positive, Ug.
I would advise to find a way to get that 2 wire roid or a Wema/Kus sender working.

The 3rd wire (red) was not used as the Centroids only had Send & Negative terminals.
The sender tube (shown from EF facing aft) OD is only 1 1/4 and although I didn't measure the KUS float it appeared there was no way it would fit. Perhaps if they could make one longer with less diameter it might have a chance as long as it didn't get hung up. I see their US address is near here so just emailed them. A long term fix IF the tank was empty would be plumb a 2" tube instead but at this point plan A is try a new Centroid sender. Their tech these days, Joel, wrote me the 3 wire ones work best with VDO's and the boat already has the 3rd wire. I recall running a 3rd wire when I installed the Centroid decades ago in the previous Bert and did the same with the new one I put in the Contender after the OEM with the arm float got stuck leaving me and the GF adrift 8 miles offshore. Funny thing about that was I had been thinking the HPDI's got really GREAT gas mileage as the gauge on that new boat had been showing 1/2 for a long time.

Whoa,
That tube goes to the bottom of the tank?
Is a return hose also attached?
Don't think you want a float sender with return fuel pouring over it.

Instead of bad mouthing roid any more,
Since I was a kid, Rochester has always made good stuff.

https://rochestersensors.com/products/fuel-oil-level/capacitance/

Some of this stuff new last year.

Actually not sure what the fuel line in photo is as I thought another line about 2 ft. away was a feed and the return about 2 ft. in the other direction. I believe that tube connects at the bottom of the tank. Bad me for not paying more attention when I had mechanic here changing fuel lines although the one shown was not changed for some reason. I think he would have had to cut an access hatch in the deck as it goes into the top of the tank a few ft. away. Maybe its a vent of some sort? After topping off the tank last week and later removing the sender when it continued reading only 1/4 saw the fuel level in the tube was about 5 in. from the top which is about the top height of the tank. In thinking about this more now, will have to take a closer look at the lines as now I'm wondering why only one at the top was changed and where is one for other engine. The forward tank has two return lines and the feed at the bottom. I think the feed must have a T but will have to explore that one too now.

Update. No one at Centroid picked up phone to place order. Rochester only sells via their distributers one of whom is Sam's who said theirs will not work but they had 5 Centroid's in stock. Now they have 4 and told them they need to add some Bertram photos along their wall of Hatteras photos. Evidently the 3 terminal one, only 1/2 in. shorter is a stocked Cabo part and until I brought them up to date, they had no idea some of the items they had on display were also Bertram items.

Viking
Carver
Contender
And more

Their little store had about 20 photos of Hatteras's along a wall but no others. Back to trouble shooting as the sender showing E when tank is full. Grrrrrrrrrrrrrrrrrrrrr Sure wish I could fit a KUS in the tube.

Bass Ackwards gauge.
Re-read post #38.

The VDO gauges are all new and rated 240-33.5 ohm. Before installing the new KUS sender in the fwd. tank I laid it on aft deck and attached the send & neg. wires. Moving its float properly moved the needle on the gauge. The new Centroid I got today is the 3 terminal version also used in previous Bert for like 30 years with no issues but I discovered some strange voltage on the red wire; specifically 188.00 DC. Finding that hard to believe I hooked up a different digital meter but it too showed the same voltage. According to the troubleshooting sheet on the Centroid site it should be about 12.5 volts DC. No idea where that wire feeds from so I'm thinking of running a temp. test 12 v. wire instead. PS. When at the store today when telling the guys about the tech at Centroid believing my original sender was bad, made a comment, "you actually had him try to help. I can't even get them on the phone."
Plane B. I'm thinking there must be a shut off valve at the bottom of the tank and if so should be able to replace the existing vertical tube shown in post #45 photo with a large enough diameter one to accommodate a KUS sender's float. Hard to believe this boat came to me with so many of the various tanks senders with issues. First was the fresh water, then the Grey water, and now BOTH fuel tanks although the fwd. is now reading fine.
By the way; I believe that fuel line shown in the # 45 photo is there to vent the tube allowing fuel level to rise as fuel is added.

That does make a lot of sense.

I thought it does. If there was no place for the air in the tube to go the pressure would prevent the
fuel from rising. Anyway, it is what it is. Bertram's design.
The tech said the red wire MUST have 12 volts so the hunt begins as to why it does not. Hopefully an easy fix. but sure would help if the Bertram Manual had a diagram for them.

188.0Vdc is just noise. Wire probably dead. Was your ing/run key/switch on? Can you trace that wire?

Switch was on. Not yet known where that wire comes from but I would think up on the bridge.

Switch or Switches? On our Bert, each engine run switch goes to one of the two tanks.

Same situation. Starboard engine switch also powers fwd. tank and Port the aft tank sender. Long story short finally learned the new sender was bad so went back to Sam's & exchanged it. Newest one working. Tech at Centroid said both gauge & sender needs to power on same time or risk sender doing an auto recalibration and also that sender good on both 12 & 24 volts. You're right about that Mary, who tried to tell me the Cabo sender would not work on Bertram. The only difference is the Cabo one is 27.5 in. and the one High Tied showed for Bertram was only 25" so the reserve would have been even more, plus he wanted $40.00 more.

Wow, another 'roid DOA,,, Surprise... (HA).
The kid at 'roid could cut them to length.
Sam's already has them to length required for their Hatt models. Sam's probably had a big order discount when they ordered/purchased them,,, many years ago.
Probably before the kid purchased the remaining Centroid company and inventory.

So, what is your actual tank depth?
And what final length did you end up using?

Glad you finally have some tank senders working.
Let's go test them out,,, Let's go fishing..

Sam's said they only had 5 of the one with the Cabo part number that I got. The bad one that first came out is 28." I think the tank is 29" so the 27.5 should be fine. The other tech that replaced all the gauges & 3 panels on the bridge and ruined one at the time, got the new replacement today after waiting 4 weeks and will be back with it Thursday with the gauges installed ready to wire in. Might actually leave the dock one of these months.