If you are using saltwater to flush the toilet the salt can build up after time and turn a 1 1/2 in hose into a 1 inch or smaller hose. One trick you can try is vinegar. Pour it down the toilet then let it sit for a while then try to flush it down. You can also use channel lock plyers to squeeze the hose to help break up the harden salt. You can also try boiling water and do the same.
The main cause is a clogged vent. If you over fill the tank or go out in rough water with a full tank, it can slosh around and clog the vent. It's a simple fix. Remove the vent hose, it's normal just a hose clamp that you can remove with a screwdriver, if you hear air blow out... it's the vent. Sometimes you can use a foot pump for a dingy. Stick the end of the pump in the hose then give it a good pump and hopefully the fixes it. If not, disconnect it from the thru-hull fitting. Try to use something like a pencil to poke thru the fitting on the tank and the thru hull fitting to make sure those are clear. Sometimes there is a small screen on the fitting going out and that can clog up. Now take the hose outside and clear it with a hose. Make sure you get EVERY DROP out before reconnecting it.
Chemicals work but not many. Most are just coverups. We use a chemical that work very good for keeping the tanks from building up sludge on the botten. You can sign up for that here firstname.lastname@example.org put in the subject add chems.
Who fixes heads
TIM KEELER (415) 332-1072
BAY GREEN (415) 621-1393
M.oble T.railorable H.ead E.mptying A.nd D.ispersment