If the tank was originally a recirculating head system and the PO decided fresh
water flush was nicer and capped the vent by mistake and hooked the vent up to
the recirculating line going to the bottom of the tank you would have the
problem you described. Check the tank and count the number of fittings on it.
recirculating tanks have 2 big lines and 2 small lines. If you have this and
one small line is capped just switch the small line for the small capped line
and try it out.

Interesting thought, Rolf...but I don't THINK Hunter ever installed
those gawdawful recirculating systems. I've yet to hear of one anyway,
and I've been giving plumbing advice on the Hunter Owners site for more
than 5 years. All the builders who did install recirculating systems
used Raritan Compact toilets and either the Raritan the 5 gallon tank
that wraps around the bowl or a 5 gallon plastic tank made by
Kracor...the OEM toilets on 70s and early 80s Hunters were
Mansfield/SeaLand 751/752 manual toilets and their tanks were all aluminum.

But even if they did, it's unlikely the original tank would still be on
the boat. The toilet has definitely been replaced, and if the PO who did
that ever intended to use the tank, it would also have been replaced
with a larger one...'cuz once it was converted to use flush water
instead of recirculating waste water, a 5 gallon tank would fill up in a
day. It's also in the wrong location to have been part of a
recirculating system.

But as I said, it's a very interesting thought...I'm surprised anyone
today even knew that those systems ever existed.

--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://69.20.93.241/store/customer/p...40&cat=&page=1