Fuel tank filling and gauge

Hi folks,

I've got a couple questions for you experienced and knowledgeable manatee owners.

My fuel gauge has never seemed to be 100% accurate. A few years go I replaced the tubing from the back of the gauge to the top of the tank and hoped that would resolve it but it seems that maybe the diameter of the hose is slightly larger and possibly affects the reading or there is a small air leak.
What is your folks experience? It seems a site gauge on the tank would be a better alternative. Has anyone had this issue and how did you resolve or improve on it?

I'm curious if others have had any issues taking on fuel on their Manatee. The horizontal run of the inlet hose to the top of the tank seems to be very easy to fill up if the fuel hose pressure is too much. I noticed that quite a while back so I'm always slow to take on fuel pumping and waiting a bit then pumping some more..

In the past in an attempt to get a better idea of the tank level I have disconnected the filer hose from the top of the tank and dropped a string with a nut tied to it until I heard it hit the bottom and pulled it right up to see where the fuel was on the string. I know the tank is not flat but at least I could get an idea of how far up the fuel was in it.

I keep a log on engine hours so I can guesstimate fuel consumption as well but I recently installed a new Webasto diesel heater and haven't been as good about tracking hours used so I can't estimate consumption as well.

I wanted to top off the tank cause I figured I'd been using the heater quite a bit but did it the poor mans way - a couple of 5 gallon jerrycans and a little Shaker Siphon hose. The first 10 gallons went in fine but the third one gurgled up a bit. It didn't splash out but I could hear it and then looked inside with a flash light and saw fuel. I wouldn't think the siphon was much pressure to cause the horizontal run to fill up so fast but apparently it did. My gauge of course reported 3/4 a tank so I'm not sure if I overfilled the tank or not.

Today when I opened the hatches to go down and use the string method to check the level I noticed some diesel on the absorbent pad in the engine compartment bilge. I've never had that before so I immediately turned off the bilge pump, shut off the main on the fuel tank and I checked the hose run and fittings and hull but couldn't find a drop. Now I'm checking the filters and haven't been able to find a drop. Any ideas where this fuel could have escaped from? I'm wondering if I did overfill it would it have traveled back thru the return line? I'm hesitant to remove the hose from the top of the tank to check the level in case it spits some out until I have a helper around.

In the meantime I'm hoping some of you folks might have some thoughts to share. I'm due for a haul and wanted to schedule it this month but I'm at a standstill until I figure out what happened here and if there is anything else I should check or be concerned about in regards to the fuel system. Obviously this is critical to determine. My first concern was a tank seam leak but after placing absorbent pads and inspecting with a mirror and flashlight I didn't see anything on the underside of the tank (thank god) There was however a little fuel again on the new absorbent pad.
Any ideas are GREATLY appreciated.

Are you referring to a tank tender bubbler with the little pump knob? Those are pretty good, but any leaks are going to mess up readings. If you hold the button, pump, then stop pumping- and reading decays, you have an air leak somewhere. It is normal for it to drop a tad after you quit pumping, but then it should stop and hold reading.

Size of hose should not matter, it just means more pumping.

Last passage I was on the tender was flaky. I put a few drops of engine oil on the pump shaft. Some of that oil made it into the valves and the reading decay went away completely!! I think the oil plugged a micro leak somewhere.

If you can easily add sight level hoses in the engine room, that is always nice to have. If you doubt your tender reading, you can go in ER and read direct.

Hi Ski, It's the original Krogen gauge that I guess function similarly or the same to a tank tender that uses pressure without a powered sending unit. There isn't any pump that I'm aware of. Yes, I'm looking into some new alternative gauges including a site glass or hose for when I haul so I have more accurate readings and can avoid this mess. The water tanks are the same gauges and they don't work well either. I'm really more concerned about the fuel leak at the moment and any impact overfilling could have had on my engine, but thanks for the term tank tender. Here is a pick of the back fyi (hopefully)

Look for a pump. That kind of level gauge needs a source of air from somewhere.

Thanks Ski,
I looked under the salon couch access area and did not find any kind of pump for the gauge. It connects to the top of an access port to the top of the tank. I had my fuel polished a few years ago and this was the location that was used to access the tank.

I did find something else - a second fitting on the tank port side with a hose that seems to go over to the scuppers drain. This is not visible from the engine compartment as it's behind the firewall. This "vent" was probably the source of the gurgle sound I heard and where the diesel came from. It's clear to me now I overfilled the tank. I need to either fix this fuel gauge so it's accurate or get a new one.

Is anyone familiar with the original Krogen fuel gauge? There isn't any MFG name on it that I can see but someone might recognize the emblem on the face of it.

Might be a "medallion" brand?? If not too difficult, pull sender out of tank and see what it is.

Can you trace capillary tube all the way from tank to gauge?

Never seen that system.

Yes I can pretty much see the whole tube but it's tight to inspect properly without removal. Looking around online I found a similar solution at "thetanktender" that explains installation of there unit which I think works off the same principal -air pressure. Has a pump right on the face of the gauge. West has them but they are a bit pricey 4 tank gauge is over 700.00. If the tube has a leak or kink it can be replaced Grainger is a source and I think it looks like 1/8 but not sure until I cut a piece off and measure it.

Before I open that access plate I'm going to burn off/ tap off some fuel. I've had enough of diesel for a bit. I'll be back down there when my new filters come in unless I go get some aftermarket ones from Napa.

Thanks for your replies Ski, much appreciated.

Hart tanktender is about 400bucks for 3 or 4 tanks. Might be a nice upgrade. At Defender et al.

Funny, I just did a quick check at the time and the $750.00 was West Marine's price. If I do upgrade I'll be price shopping but thanks for the tip. It did look like a nice unit and at half the price it's more attractive. I was going to think about how I could add a site tube of some sort in addition to a new/ repaired gauge. Something to ponder. Thanks again.

Don't give up on what you have now, yet. But if you do, you'll still have to go through a major tank calibration with Tanktender. You carry 280 gallons of fuel and the tanks are not rectangular so the gauge is not linear and tank level gauges usually are.


We have a Tanktender for 2 tanks and love it. When we did the calibration, we used a 5 gallon bucket. At 17" it's full with 150 gallons, at 8.2" it has 45 gallons left.


Since it's a factory gauge, Krogen should have all the information and if it's not, send a few PMs to the other Manatee owners on the forum for your tank configuration.

Greetings,
5 gallon bucket? Holy crap that's over 160 buckets for me. No thanks. I'll stick with the dipstick.

Fuel sight tube

CaptGrail This is the setup we have on our fuel tank. I lift the deck hatch when fueling and can easily keep and eye on the level. It doesn't look like it was added by a PO to me.
The starboard water tank vent and fuel tank vent are near the fills on the starboard side on our Manatee. I always block the deck drain in that corner when fueling in case of burps.
Also the port water tank has a similar sight tube, we cross connect both tanks so one sight tube works for both tanks. In the photo the clear tube that is below the stringer angling up is the sight tube . I extended from it location on the aft bulkhead so I can check the level from the galley deck hatch. This extension was a trial to see if it would work, I plan on installing tubing "L" fittings to position the sight tube to a more vertical set up. We have a 5 KW Northern Lights generator in that location so access is very limited, as you can see the generator start battery, hot water heater, potable water pump with expansion tank, auto pilot hoses and valves, etc makes it a very busy and cozy area, I use a seat cushion and do all maintenance lying down. It lovingly has been named the "snake pit"
Bill

After scouting around in my engine compartment, I found the fuel vent hose behind the soundproofing/insulation. Sure enough, it was shot in one area - the bottom part of a anti-spyhon bend which probably ended up with fuel and degraded it over time. The vent line connects to a single fitting on the port side top of tank. The line runs over the top of the water tank and back to the aft deck vent fitting mounted in the fiberglass right next to the teak vent, port side as does the water tank vent. Starboard side has only one vent for water. (Fyi, for clarification, behind the teak vent starboard side is an anti-syphon vent for the exhaust system.)

Now I'm contemplating how to make a sight gauge with just the one fitting on top and one on the bottom. Maybe I can T off whats already there..
Bill on your setup - why the shut off at the top? You must have another valve below that feeds your larger fuel strainer for the engine. I'm guessing that other smaller strainer is for a generator or something else? Reading a few other posts re:site gauges it looks like I'll need some fuel resistant pvc or tubing and some t's. The top appears to be a hose clamp to an elbow, the bottom is compression fittings.

Some folks debated over needing shutoff valves online but I wonder if that is really necessary in this case. If the main is open there are more than several places that could have leaks potentially so why call out the site tube as being any different? Maybe if it was glass and subject to breaking but other than the clear tube discoloration if a diesel resistant hose was used why the need?

The bottom fitting already has a T one side to the Racor and on to the engine, the other goes to a second strainer starboard for the Webasto heater and back towards the main and into the galley bilge (snake pit ;-) where the gen set is. When the main is open all these fittings are open so again, why the need for shutoffs? If I shut off the main that is it - no fuel going anywhere. Of course I don't want to have any issues with a surveyor in the future so thoughts are appreciated. Bill a photo of the bottom of your site gauge setup connection would be really helpful if you have a chance.

Thanks again for feedback.

We will get the photos for you Tuesday when we do our Winter weekly check on the boat. I think the ball valves top and bottom are there to isolate the tank when changing the tubing. The small Racor is for the generator and yes there is a shut off valve to the engine Racor. I replaced the tubing on the sight glass once as the clear vinyl will discolor over time. The sight glass in the photo was replaced about five years ago and as you can see it is still very clear.

If you are going to tee off the main engine supply fitting at bottom of tank, do put an isolation valve for the sight gauge alone. That way sight gauge can be isolated with engine running. So should it leak you can close it off and keep going. And if by some strange reason the tank pickup got clogged, sight gauge would suck air. Remote chances, but should be easy to add a valve while building system.

And do connect the top of the sight hose to the top of the tank. That way if pressure builds in tank for any reason, sight gauge won't spew out the top. No big reason to put a valve on the top of the sight hose. It can be teed into existing fittings.

Fuel Tank Sight Glass

Capt Grail, here are the photos of my fuel tank sight glass fittings. I hope you can see that from the fuel tank valve there is a elbow to which I added a tee for the Gulf Coast filter fuel supply and above the tee is the sight tube barbed fitting.
To the right and below the fuel polisher blue hose is the fuel tank suction valve, it has a tee to supply fuel to the engine Racor and generator Racor fuel filters. So this tank has two threaded fittings on it's bottom.
The top fitting on the sight glass photo blurred, probable to close to focus, it is a ball valve like the bottom, an elbow and a hose barb fitting.
The sight tubing is clear vinyl and the barb fitting is only wide enough for one hose clamp, but since the fuel is not under pressure and there are shut off valves top and bottom it is not a safety hazard, and passed a surveyors inspection.
The two black hoses with chafe guards are the engine water jacket hoses to the hot water heater coil.
Hope this helps.

Thanks for the photos HiDHo, greatly appreciate your efforts and info. I'll have to digest them and see what I can do with some new fittings. My gen set and heater's fuel filter is an old Dahl and I'm thinking of replacing it since filters are getting harder to find. This might make me rethink how it's connected.

Ya'll might like to check out CruzPro digital tank gauges; they use resistance, and are said to work with many (any) senders. Read out in gallons or liters or whatever, said to be calibrate-able for any shape tank.


-Chris