So what do you consider the most important things to check out on a used boat before you buy it?
How about a Top 10 things to check?
Go!

Transom and motor compression

Transom
Motor compression
Axle hubs
Tires
Trolling Motor
Everything electrical you can check (pumps, lights, electronics)

^^This plus is the title clean and ready to transfer

Spin the prop
to check for bent prop shaft

Hull blisters

transom integrity
water pump

Compression check on motor
Check Prop Shaft
Transom
Batteries
Tires
Pumps
Electronics
Carpet
Trolling Motor
Check For Stress Cracks In Every Corner
Look Under Boat For Gel Cracks
Good Luck on your next boat hope you find a good one.

http://basscatowners.yuku.com/topic/3077...at#.VTLFdRg8KrU

This is guidance providded by BassCat Boats.

As far as what to check everyone has given you solid advice. I'll tell you that I wasted a lot of time looking at craigslist and checking out boats with major problems. I wasn't expecting to find that local boat dealers had used boats IN THE SAME PRICE RANGE as the ones I was looking at but in far better condition. With a reputable dealer you know that a real mechanic has gone over the boat and the paperwork is a lot easier. (Registration, title, etc...)

Be SURE to have the boat and motor checked by a trusted, reliable, third-party mechanic.

Be SURE to have the boat and motor checked by a trusted, reliable, third-party mechanic.

Frankly, you'll find better maintained boats on here & BBC. People with trashed out, neglected boats don't sell them in places like this because the population base is to knowledgeable. They target Craig's List and hope a sucker buys it and they can pass along the problem. Make sure you KNOW the mechanic has no history/relationship with the seller. If they won't let you lake test, walk. Period. People who won't let you lake test are hiding something, plane & simple. Dealerships give you some peace of mind, but when buying a used boat without warranty, there are no guarantees. It's a black hole of money. Good dealers will work with you and try and help you if something goes wrong soon after the sale. Bad ones, will say to bad, so sad. Ask lots of questions. If the seller doesn't want to answer questions, they're probably hiding something. Don't fall in love with a boat based on color and things like that. Buy a boat based on sound principles like craftsmanship, how it was taken care of, what dealer serviced it, resale value, motor size comparable to length, etc. Take your time, don't get in a rush. Enjoy the process. When you find it, you'll know it.

Look at the hours and brand of boat. Pull cowling and look for wrench and socket marks on the motor. Any kind of non stock components. Also boats that are used often have less problems than the low low hour rigs.

I recently went through the process of looking at a lot of rotten boats before finding my current rig.

Thoroughly check the transom integrity, look for stress cracks in the corners. any flex or stress cracks in the corners of the splashwell, no deal.

Look for rot stains under all thru-hull fittings.

Check the bow and transom eyes are not loose.

Check the hull integrity everywhere. I looked at a Champion someone was selling that had an 8" gash near the bottom of the hull with wood rot stains dripping out of it. After I showed it to the owner, they proceeded to keep trying to tell me it was a good boat. All I could do is shake my head as I walked away.

Any boat with wood (generally older than 2000), get into every compartment, look everywhere, and thoroughly inspect the entire thing for any wood rot. Try to get your head inside compartments to look up at the bottom of the floor. Walk and feel every inch of the floor, feeling for soft spots. Soft spots in the floor could potentially mean bigger problems below. Even check side walls in compartments, and under batteries. Rotted areas can hide. Boats generally rot from the inside out. Any rot at all, no deal unless you're into restoring and rebuilding boats.

You may or may not be surprised at the number of times I was promised that it was always garage kept and I'd find leaves and other evidence then rot somewhere. I'd always ask the questions first even though I would find out the answer myself just to see what kind of person i was dealing with.

Compression check the engine. I'm mechanically inclined, so to me as long as compression is good, just about anything else can be fixed.

Be sure prop shaft is straight.

Check trailer tires for dry rot. You want to be able to get it home.
Surface rust on a trailer isn't anything to be afraid of, but holes from rust is cause for concern.
Ask about the last time the hubs and bearings were serviced.

Always lake test once you check it out if you're serious about buying it. Check functionality of shifting gears, steering, varying speeds from idle all the way up to wide open throttle running for a while.

This is a very short list of key things that are on my multiple page boat buying checklist I recently created.

Be very detailed and inspect every inch of it.