No alot you can check other than appearance, engine compression and the lower unit for metal shavings and water.
Loosen the lower unit drain plug catch some of the oil in a container and see what you get. The ideal situation would be for the seller to take you for a boat ride to see how the engine performs at varying speeds.
Sometime not enough hours can be a bad thing if the motor sat up to much and was not cared for properly. On the other end too many hours is not good either. ("be careful") and good luck!

...check skeg for welds...and hand turn prop for shaft trueness...I got burned before at the time when I was young and intelligent ???...cheers

a good rule of thumb is that 2 strokes have a life span of about 1,000 hours. many last longer but that's a good bench mark.

couldn't tell you on 4 strokes. i've heard stories of 4,000 trouble free hours on them but i've also heard of 2 strokes going that long.

compression check...It's only feasable to 'hire out' if you're offing a lot of money..

it happened to me, i didn't know! i bought a used 90 2cycle. it seemed to run ok to me. i took it to my machanic to have the water pump changed to be on the safe side. well, he called me up to go over there. there was whitish build up around the heads at the bottom where the gaskets are. he told me that means the engine was run hot a lot!! long story short, had to rebuild it! he said sometimes depending on the engine, compression can look good, but that doesn't necessarily mean its ok inside the cylinders. oh, and the machanic was a very good friend of mine, i have known all my life, just to let you know, incase someone says the machanic jacked me!! GOOD LUCK

Compression checks are not always reliable. I blew up my merc 40hp 2x. Both times in the top cylinder the piston rings were cracked, rod bearings were chipped, and the cylinder sleeve had slipped. Ran a compression check and it tested out just fine, bleed down too!

...another thing is look around the "bozo's" garage and yard for neatness and order...if he had any demeanor chances are unseen things were attended to w/ no cut corners ???...cheeeeers ???

p/s might even talk to his first wife ???

Ok, so a compression check is not the only thing to check out on a used motor, but, it's not like you can tell the seller - "hey, I'm going to take your boat and motor to my mechanic and rip it apart to see how the inside looks."
Is there a way to tell if the innards of the motor are bad without a complete tear down? Just curious.

Duck enticer and Abeast, thanks for the info. I thought Comp.Check was more reliable than that. That's what I like about this site, you can get good advice and free to boot...

...they right ZB...sometime the compression can go way up but only hold for a short time...think the bottom ones hold better due to oil settlement...Geronimo sez : "watch danc'n hurry-up mechanics w/ quick hands ain't no good "...cheers

but just like i said, look for the whitesh junk around the heads, this is a good sign that it has been run thru the mill!!! best bet, is to try to buy from somebody you know or somebody you know that knows the guy you are buying it from, GOOD LUCK WITH THAT!! this is no different than buying a second hand car from these honest car lots??? LOL!!

I was always told that another good visual indicator of an outboard that has been run hot is the condition of the paint on the power head; if it's blistered and peeling that's usually a good indication that the motor was repeatedly overheated. there's my 2 cents worth

I have a skeeter with a 115 4stroke I bought used and have had for over a year now. It is the sweetest running motor ive ever had. A mechanic told me they are practically bullet proof with the proper maintenance...change the oil once a year.

i have a 16 ft. alumacraft with a center console and a 60-4 cycle yamaha. it runs great, me and my grandson and our stuff, 40mph! and the fuel economy, 9 gallon tank, 4 and a half running hours! i got a 3 gallon xtra tank in it, for a spare, filled up with premiun fuel, cause it last longer than regular, and added stabil to it to make it last up to a year and have never used it yet! 4 strokes have power! the great thing is you don't have to buy that expensive 2-stroke oil, even cheaper to run!! ya, i paid about $1500 more for the 4-stroke, but you can't even tell it's running unless you look at the pee thing!! you can talk to each other and hear each other while running!! i love it, will never have a 2-cycle again!!!

When I bought my boat about 2 months ago I brought it to Ascension Marine and paid $100 to have them check the motor out. Everyone I talked to told me to do it and I was really glad I did get a professional opinion! The motor still runs great, but everyone told me to be leary of the oil injection pump (vro). So my advice to you is have it checked out and the way to tell if a injection pump is going out is to look for oil or gas around it. Hope that helps

Remington700