What you really need is a loop in head discharge
line...to provide a "hill" higher than tank contents can climb over at any angle of heel. Whether you also need a new a joker depends on the condition it's in...joker valves usually wear out in about two seasons max. However, a joker valve is only designed to prevent a flood...it can't prevent slow seepage, which means that just replacing it without also installing a loop won't keep waste out of the bowl if you stay on the tack that allows waste to flow back into the head discharge hose for any length of time. However, whether to rebuild the toilet--or even invest $8 in a joker valve for it--depends on the make/model age of the toilet.'cuz not all marine toilets are created equal. Some are build to last 100 years...some to last 15-20...and some only 5-10. I wish you'd asked questions before you installed the tank...I could have told you how to plumb it to eliminate the need for the loop.
