That sounds like odor from the tank
First thing you need to do is pump out and THOROUGHLY rinse out the tank (you'll find directions for doing that in HM forum discussions)..Next run a LOT of clean water through the toilet to rinse it out before you remove the discharge fitting to replace the joker valve. Put a garbage bag or aluminum pan under it to catch any spills. The joker valve is part #C253 in the exploded drawing in the manual for your toilet, which you can download from here
http://www.raritaneng.com/pdf_files/crown_head/L91crownheadv1002.pdf
However, the joker valve is also a part in the rebuild kit If its been at least 5 years since the toilet has been rebuilt (all the seals valves and gasket replaced...they DO wear out!), that should be done. The correct kit for a 1987 Crown Head is CDRK. If a PO has replaced the toilet with different one, I need to know what it is to know which kit is the right one.
Now...about your tank: Make sure the tank vent is completely open...scrape out the thru-hull with a screwdriver blade (or whatever works)...if there's a screen in it, knock it out...screens cause more problems than they solve. You haven't said what you're using in the tank, if anything...if you're NOT using anything, no wonder it stinks! But whatever or whether, try using Odorlos in the tank--it costs a lot less at RV supply stores than at marine stores, btw--being sure to FOLLOW THE DIRECTIONS, which means adding more as needed. If Odorlos doesn't work, we may have to modify the tank vent, which isn't that hard to do, to get more oxygen--which is the key to eliminating odor--into the tank.
Doing all of the above SHOULD solve the worst of your odor problem, if it doesn't solve it completely. Now about bilge cleaning...You said,
any ideas on how to better clean a bilge? I usually hose down everything with a garden hose and scrub what I can with Simple Green then go for a ride and let the bilge pumps do their thing.
Would you just hose down a sinkful of dirty dishwater, scrub a bit with detergent and then just pull the plug without rinsing and expect the sink to be clean? Then WHY do so many boat owners think they can end up with a clean bilge doing what amounts to the same thing??? Doesn't matter what cleaning product you use, you'll never have a clean sink OR bilge unless you rinse ALL the dirty water out! If there are areas you can't reach, buy a power washer...they aren't expensive and IMO essential boat maintenance equipment. And then use a shop vac or dinghy bailer and a bucket and sponge to mop up the rest of the water, both after cleaning and also at the end of each weekend aboard. Dry bilges don't stink.
I strongly recommend that you check out the link in my signature here...it goes to a comprehensive "marine toilets and holding tanks 101" manual that will teach you how to operate and maintain your system to PREVENT 99% of problems so you won't have to solve 'em. And also spend a lot of time reading previous discussions in this forum...some good ideas there about how to do it and also how NOT to do it! And I'm glad to answer questions too.