Trojan Boat Forum

I have a '78 F-32 with a 4-tank configuration. 3 of the 4 gauges constantly read 1/2 tank and one of them reads 3/4. The tanks were topped off before my first trip.

I am curious if there are any common issues that I should be aware of, but I am figuring I need to replace the sending units. I question if this is even possible without removing the tanks and if so, where to source the parts (yes, I checked with Beacon).

Do the fuel gauges read 1/2 or 3/4 when the ignition is off? If so, the gauges are probably broken. The gauges should read < E when the ignition switch is off and no power is being supplied to the gauge. When I bought my boat, both fuel gauges would read 1/2 whether the key was turned on or off because the gauges were broken. You can test your gauges by jumping the signal terminal to the ground terminal when the ignition is on (12V power being supplied to the gauge). The needle should deflect all the way to the left or right (depending upon the resistance values of the gauge). If the needle doesn't move, the gauge is broken.

If the gauges are broken, it may be difficult to find a replacement gauge that matches the resistance values of your senders. The best approach would be to replace both the gauges and senders. I ended up keeping the original senders (because I didn't want to go through the hassle of replacing them) and replacing my gauges with European standard fuel gauges. I calibrated the gauges by adding fuel 5 gallons at a time (I have (2) 30 gallon tanks) and marking in pencil where the needle was. I then put a "1", "2", and "3" on the gauges to correspond to when I have 10, 20, and 30 gallons remaining. Basically, 30 gallons (full tank) is at the 3/4 mark on the gauge, 20 gallons is at the 1/2 mark on the gauge, and 10 gallons is at the 1/4 mark on the gauge. Using my calibrated marks, I can estimate how much fuel I'll need to take on at the fuel dock pretty well.

Before you start replacing your senders, make sure your gauges are working. Gauges are a lot easier to replace than senders.

bjanakos wrote:I have a '78 F-32 with a 4-tank configuration. 3 of the 4 gauges constantly read 1/2 tank and one of them reads 3/4. The tanks were topped off before my first trip.

I am curious if there are any common issues that I should be aware of, but I am figuring I need to replace the sending units. I question if this is even possible without removing the tanks and if so, where to source the parts (yes, I checked with Beacon).

You can get the sending units out very easy, aft tanks a snap , with the forward port and stbd take your time, may have to bend arm a little to remove because below the salon floor deck but a few minutes never the less.....if I remember right they were somewhere from 90 ohms, it is stamped on there.........now the old ac gauges did not work with the new tanks I put in,new gauges and all is well....Mike

The gauges do jump when the ignition is on, but it seems like the point is moot if I need to replace them anyway.

I did find an older post that referenced a replacement fuel sender. For $20 it's worth a shot.

I would check it like dog house said . just ground the sender wire and see what the gague will do . if you get full movement ground vs not then most likey the gague and wireing are ok and the sender is bad .

Remember the sender must match the gague (ohm range )

When I replaced my senders I up graded the senders to wema senders . They are now dead on . much better then that swing arm junk


http://www.trojanboats.net/wforum/viewt ... ema#p84798

Wema to the left junk (swing arm ) to the right .

I replaced all senders (5). Two fuel, fresh water, black water and gray water. They work great... Great quality.

How do you figure the length on those? Just measure the tank and get the one that best fits?

Also, how do they wire up? Mine only has one lead. I am figuring that the negative side gets it form the tank.

bjanakos wrote:How do you figure the length on those? Just measure the tank and get the one that best fits?

Also, how do they wire up? Mine only has one lead. I am figuring that the negative side gets it form the tank.

Ok, so I think I answered most of my own questions... I'll have to take some measurements on my next trip down there. Maybe I'll buy one of these and give it a try.

For what it's worth, there are some 5" holes drilled in the floor above the forward fuel senders, so perhaps this has been done before.

I forgot to say I used WEMA senders and gauges. My fuel tanks are the original 63 gal galvanized tanks, and I think I used either 19" or 19.5" senders. Before anyone comments that I am crazy for putting the old ones back in, they were removed and cleaned without a speck of rust on them. My water and holding tanks are Todd plastic 35 gal. Those are 12" senders. WEMA will answer questions over the phone, good customer service.

bjanakos wrote:How do you figure the length on those? Just measure the tank and get the one that best fits?

Also, how do they wire up? Mine only has one lead. I am figuring that the negative side gets it form the tank.

Measure the tank depth and use 1" shorter unit . 2 wires one to ground and one to the gague . The Wema diagram shows pink to ground black to gague but it will work both ways .

Bubbabuda wrote:I forgot to say I used WEMA senders and gauges. My fuel tanks are the original 63 gal galvanized tanks, and I think I used either 19" or 19.5" senders. Before anyone comments that I am crazy for putting the old ones back in, they were removed and cleaned without a speck of rust on them. My water and holding tanks are Todd plastic 35 gal. Those are 12" senders. WEMA will answer questions over the phone, good customer service.

Was that on the round tanks in the rear? I measured 19.5" from the inside of the seams. I'm thinking for grabbing an 18.5" sender.