I have a 2014 with the Volvo Penta. You didn’t mention what engine is in the one you are looking at . As already noted they are easily to launch and retrieve solo and general maintenance is a breeze as everything is out in the open.
Also as you stated they are slow. IMO opinion they are also noisy but not much you can do to change that with a 3 cyl diesel.
A couple of things I would look at if I were checking out a new to me used 21EC.
- if it’s on a trailer I would look at the cutlass bearing. Grab the prop and give it a shake up and down side to side. There should be little to no movement.
-At the coupling area try and turn the shaft by hand. It would indicate that the drivetrain to shaft alignment is at least close if it rotates easily. I check mine regularly and can rotate with just a thumb and two fingers.
-if taking it out for run I would run it up to temperature at cruising speed and then run it at WOT for 5 to 10 min. There should be no white steam coming out of the exhaust discharge. If there is then it would indicate issues in the raw water cooling system,,,,impeller, exhaust elbow or the heat exchanger itself.
-Take a look at the engine mounts to see if they look OK
I’m sure there are other things but those are a couple of important ones with regards to the engine.
I use mine mainly for ocean fishing and love it. You won’t win any races but you won’t break the bank when fueling up next to those bigger boats. I have around 3400hrs and no major issues so far.
Finally if you do decide to purchase this boat you will find no better source of helpful information and advice than what you will get from the kind folks on this forum.