holding tank sensor

[need low boom]

I have a 1980 323 with 40 gallon holding tank and am need to replace sensor that lets me know when tank is2/3 full. Does anyone know where I can get one. It was made by
CELANESE.

[Dolce_Vita]

Wow!  40 gallons!  The stock 323 came with a small 10 gal holding tank as standard.  And 10 gal is WAY too small for cruising (don't ask me how I know this!)

The 323 came standard with two 19 gal water tanks in the port and starboard sides in the main cabin. A 40 gal water tank in the bow was an option, so I suspect a previous owner either converted an existing water tank into a holding tank, or installed one in the bow locker space that was otherwise there.

My point is that this was a custom installation.

That being said, your best bet is probably the R/V supply world, where such sensors are common.
Here's a link to one kind of sensor that claims to be proof against fouling that causes false readings:

http://www.rvprobes.com/howitworks.html

If you end up replacing the whole sensor system, Garnet Industries has non-contact sensors that go on the outside of the tank and are immune to fouling:

https://www.garnetinstruments.com/rv-shop/products/

[need low boom]

Thanks. Boat is from East China Township on St Clair river. The holding tank is in the bow and is stainless steel. There is no Y valve. I guess they are very strict about pumping overboard in Michigan. Most boats I have been on have the Y valve

[Dolce_Vita]

Yes, I understand that on the Great Lakes, you can't just have your Y valve locked off, it has to be physically disconnected from the thru-hull, and both ends sealed off.