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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 11052
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a '89 Hunter 34 with a Jabco toilet - which refuses

Customer Question

I have a '89 Hunter 34 with a Jabco toilet - which refuses to completely pump out, and backs up (overflowing at one point!) waste-contaminated water into the toilet (up to a certain point, currently). I'm new to sailing and this boat, so please respond in kind. TIA
Submitted: 2 years ago.
Category: Boat
Expert:  Jason replied 2 years ago.

Good morning, my name is ***** ***** am I speaking with?

Are you trying to pump overboard, or into a holding tank?

Customer: replied 2 years ago.
into the holding tank (I think - the valve for this is unmarked and no directions are available . . .)
Expert:  Jason replied 2 years ago.

Is the tank full? When was the last time it was pumped out?

Customer: replied 2 years ago.
Tank was pumped out a couple of weeks ago, used maybe twice since then (once by a novice who took a LONG time to exit. . .)
Expert:  Jason replied 2 years ago.

Have you tried pumping it overboard to see if there was any change, or if it pumped out correctly?

Customer: replied 2 years ago.
nope - will try that now . . .uh-oh. When I tried to switch the valve, the toilet began to fill up!!
Expert:  Jason replied 2 years ago.

Which toilet do you have, what is the model number on it? And is it manual or electric?

Customer: replied 2 years ago.
manual, may be model 752 - that's what's listed in the original Hunter manual . .
Expert:  Jason replied 2 years ago.

Click this link, is this the head you have?

Customer: replied 2 years ago.
very similar - except that the pump cylinder leans a little forward rather than vertical. The remains of the service kit indicates###-##-####and the package has a check mark at the 1998 model rather than either 1986 or 2007. . . .
Expert:  Jason replied 2 years ago.

Typically speaking if it won't pump out overboard the pluming is simply clogged. When this happens what you do is get a 5 gallon bucket, fill it up with seawater. Fill the head up. And just start plunging to try to push it through. Have you done that yet?

Customer: replied 2 years ago.
Not yet - is the "overboard" setting the one where the toilet tries to overflow??
Expert:  Jason replied 2 years ago.

I don't know without seeing it.

Customer: replied 2 years ago.
Here's a picture - at this setting, toilet just backs up to existing level - at other valve setting, toilet attempts to overflow. . .
Expert:  Jason replied 2 years ago.

I'm going to opt out of this quesiton, without being in front of the boat it's just to hard. If one of the other guys has any ideas they will jump in. Good luck.

Expert:  Tan replied 2 years ago.

Does this look more like your flush assembly?

Water backing up in to the bowl is a bad Joker valve. The bowl will not empty with a bad Joker valve. The Joker valve is a one valve that only allows the water and waste to flow one way.

The Joker valve is # ***** in this pick. Remove the discharge outlet fitting # ***** to access the valve.

It shouldn't matter which way the valve is facing the head should still pump out. When you have a Y valve it is either for overboard discharge or tank discharge. The over board side will allow water to flow backwards if the Joker valve is bad.

Here is a diagram of the way yours should be plumbed.

You just don't have the MSD.

Post back with findings.

Customer: replied 2 years ago.
That looks approximately the same as my head. I tried the 5-galllon strategy that Jason suggested (on the overboard side, I suspect, as it was definitely "against the current") but the toilet immediately filled back up once more. When I switched the valve back to "holding tank" I could no longer pump at all, and the floor near the Joker Valve (very insensitive nomenclature, I think!) began to show signs of leakage. I'll try getting a new valve at WestMarine and attempt your suggested fix ASAP. Thanks!Dave
Expert:  Tan replied 2 years ago.

Ok Dave it is possible you have some blockage in the line going to the tank.

The largest issue with marine heads is people don't use enough water or pump long enough to evacuate the lines. What people do many times is pump the waste till it is out of the bowl and stop pumping. Now depending on how far away the tank is the users should remember there is no gravity in these systems it is strictly pump pushing the waste. So you have to keep pumping till the waste gets to the tank. If the waste stays in the line it starts to get hard as the water eventually flows away from the waste. Then it gets hard and clogs the line. If women use the head no feminine products go into the head it will clog.

Post back with findings and questions.

Thank you....Tan