Sort of difficult to give you any advice because you do not give specific info. Assuming you have a Jabsco
37072-0094 or similar which is mounted on the side of the toilet...
These last about 2-3 years before the seal starts leaking. In 4 out of 5 tries, replacing the seal did not work because the damage was already done.
If this is the type of mascerator pump you have, and you plan to keep the boat more than 3 years, it would not hurt to buy a spare. If you do not need to install it now, you will withing 3 years.
Before removing the old pump pump out all the water
in the toilet...you may need a shop vac to do this. Place a 20% solution of Clorox/water in the toilet for 30 minutes, then pump that out. When removing the pump, be prepared for about 1/4-1/2 cup of water
which you did not get out. Place the now removed pump in a bucket and take it to where you can first clean it with Clorox/water then inspect it. The blades on these pumps are problematic as well as the seal. If the nut holding the blade is stripped, not much you can do, but replace the entire pump. When re-installing use some silicone grease on the O ring and tighten, but do not over-tighten the pump. It is sometimes difficult to align this O ring and get the proper tightness...it may take several tries before it seals
without leaking...to check for leaking you will have to add water...if it leaks
, start over again. Be careful that you do not reverse polarity, because reversing polarity reverses the motor
and blade...The pump will not work properly with polarity reversed.
Hope this helps.