I guess I'm the oddball. If I saw a boat that I really liked better, that runs great for $5-8k I would absolutely do that. Motors run for decades, typically. Not much of a worry, for a 2010, but insist on a test ride and watch and listen carefully.
I got away from tillers years ago and I love not being twisted around in the back of a boat. Much better comfort, visibility and control.
Whether you like your current boat or not, you need to do a simple compression test on your motor. Takes 5 mins. Auto parts stores loan testers free, or you can buy one for $25 or so.
Pull the spark plugs, plug the tester in each hole and crank it for 4 seconds or so. The cylinders should be over 100 PSI and all within 10% of each other. Not sure of your exact motor type, so can't give you a good number to look for. My older 40 Merc 2-stroke ran at 125 PSI, but some 4-strokes run 150 PSI+. So just make sure they are close in PSI. Also, make sure your engine is turning over at normal starter speed, or it can throw off the test.
Since you were having lower unit issues, that may be the problem. Unbolt the lower and start it up for a few seconds. If that terrible sound is gone, buy a used lower, slap it on and then decide.
I've gotten a couple of "bad" motors in on trade that turned out to be a bad lower. I currently have a 2008 Mercury 25 fuel injected motor that was locked up, trashed, supposedly. I pulled the lower, and it's perfect. New lower costs about $250 on Ebay, when I get around to it.
I would do that before deciding UNLESS you want to justify getting a new boat or motor, in which case, just do what you want, and test it after the fact.
