Black water sender or indicator

Shaps

Well-Known Member
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Nov 4, 2019
2,456
Long Island,NY
Boat Info
2010 Sundancer 500
2015 Brig Falcon 330T
Engines
Twin Cummins QSC550 w Zeus Pods
Last week after pumping out, my indicator didn't read empty. First time since I own the boat. Tried flushing the tank with water and pumping it out again but no help. This morning, prior to pumping out, got the indicator to read 1/2 but still no luck getting it to read empty after pump out.

Stuck/clogged sender or has the indicator gone bad?
Is there a way to test the indicator?

Thank you!
 
It's most likely the sender. Unscrew it from the tank (it is messy job), pull it out and clean all 3 senders. Old toothbrush and a hose work great. However, on my boat the empty sender was too low in the tank and would never light up as the tank would never get that empty. I had to adjust it. Easy, you just unscrew the white tube on top the sender top, pull it up a bit, and tighten.
 
It's most likely the sender. Unscrew it from the tank (it is messy job), pull it out and clean all 3 senders. Old toothbrush and a hose work great. However, on my boat the empty sender was too low in the tank and would never light up as the tank would never get that empty. I had to adjust it. Easy, you just unscrew the white tube on top the sender top, pull it up a bit, and tighten.

Oooof... was afraid of that. My generator sits on top of the tank. If it's the sender I don't think it's coming out anytime soon.
 
Then you might try gently knocking the sender ring with hammer or similar. The senders are actually floats. Gently knocking might jiggle it loose. Or you might try Noflex digester (search it here) to try to clean/free them up. May take a few times.
 
Thank you @LMBoat !
I have always used noflex. Huge proponent.
Just climbed down into the ER. Looks like maybe there is an access panel under the generator. Not enough to remove the sender (potentially) but at least lift it up and shake it loose maybe?
PXL_20220814_130439677.PORTRAIT.jpg

That round circle secured by 1 screw?
 
PXL_20220814_144911799.jpg
20220814102324820.jpg
access panel out and found the senders. Looks like 3 individual senders but I am struggling to loosen the cap. Literally no angle....
Going to take clean up the scrapes I've given myself so far. Yep, that's blood in the first picture..
 
View attachment 132061 View attachment 132062 access panel out and found the senders. Looks like 3 individual senders but I am struggling to loosen the cap. Literally no angle....
Going to take clean up the scrapes I've given myself so far. Yep, that's blood in the first picture..
That’s a tight area, might be better to just replace with the kind that mounts to the side of the tank and reads through the side for tank level.
 
Thanks for the pics, and yes that is tight. A big pair of channel locks or a strap wrench will help loosen the cap. Or you might try loosening the collars on the sender tubes and shake up and down to to loosen the floats. In general, I've found this sending unit situation to be relatively trouble free as boat systems go. Only a few issues in 20+ years of owning this system on 2 diff. boats. Good luck, and keep us posted on what you find.
 
Thanks @LMBoat
I tried my channel locks with no success...
Im thinking of making an additional access hole so I can get me hand on the cap squarely..
I will definitely report back.
 
How about cutting open the plywood circle closer to the forward edge, which may give you better access to the cap, assuming a larger opening won't compromise the integrity of the platform? You then you can fabricate a piece of plywood to cover the new opening.
 
How about cutting open the plywood circle closer to the forward edge, which may give you better access to the cap, assuming a larger opening won't compromise the integrity of the platform? You then you can fabricate a piece of plywood to cover the new opening.

Effectively what my plan is... Just need to see where it all lays out. I don't see it weakening that platform at all.
Thanks @Captsteve427
 
Effectively what my plan is... Just need to see where it all lays out. I don't see it weakening that platform at all.
Thanks @Captsteve427

Personally, if you pull the old one out to check, might as well replace it. Not that big of a deal at that point. You do have to manually set the levels though. But you would have the old one to compare to.
 
Personally, if you pull the old one out to check, might as well replace it. Not that big of a deal at that point. You do have to manually set the levels though. But you would have the old one to compare to.
@SKybolt
I don't think i will have the clearance to fully remove it.
At this point, *IF* I am able to loosen and remove the cap, i think i will have 4-6 inches of clearance from the top of the tank to the bottom of the generator. Hoping I will able to shake it and see if i can actually make it read empty again.
 
@SKybolt
I don't think i will have the clearance to fully remove it.
At this point, *IF* I am able to loosen and remove the cap, i think i will have 4-6 inches of clearance from the top of the tank to the bottom of the generator. Hoping I will able to shake it and see if i can actually make it read empty again.

Those tubes are flexible, you are most likely going to have to remove it to clean it. But if not, get the hose as close to the floats as possible and blast them. I have replaced these a few times in my life and have never had success in cleaning them. I believe the inner reed switch goes bad and is why they don't work. But lets hope cleaning them is all that is needed.
 
Also, as you have seen, the 3 tubes that go down into the tank are relatively thin, and the hole is big. From the beginning, you probably have a 45 degree angle to remove them, and as SK notes, there are flexible to give you more room. you might be able to get them out.

Also, they make a "90 degree" strap wrench that might work to loosen the top.
 
I took a long handled screwdriver and placed against the notches and tapped a few times. Once it started to move, it was very easy to unscrew.

Bennett
Thank you @bbwhitejr
I was on the same track and tried that. I needed a longer screwdriver.
 

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