It will be hard to find a boat with an outboard AND a hot shower. Most (none) of the boats in your size/price range will not have a real shower. It''s easy to add a shower sump and a hand held shower nozzle.
I purchased a boat with this arrangement and found it is easier to wait and use a public shower if possible. The boat gets humid and the heads on these older boats just are not designed to work that way. Water will get everywhere. I hang a shower curtain in the head but it still doesn''t stop all the spray.
Don''t be tempted by a shower that drains into the bilge. It will stink and clog your bilge pumps. In fact you will be amazed at how bad it will smells. So will other people
I have also seen sun showers plumbed to the head for hot water, but you still need the shower sump.