argonaut wrote: The outboard represents $4-9K of the boat's value depending on age. Get the best one you can afford. All others things equal you want reliability. Open the motor cowl and look for a carb. Reject any boat you find them on.
I think the outboard represents more like $1-9k (maybe even 0) depending on type/age.
The most reliable boat motor I have owned was the Tohatsu 50-- carbureted 2-stroke. 4-strokes are less forgiving than 2-strokes and thus are more finnicky when it comes to carburetion. EFI on a 4-stroke is a must in my opinion, unless you religiously ensure it is operated regularly and stored dry. Even then they must be adjusted or you risk stalling/starting problems. The Tohatsu I had started and ran everytime no matter what. Well, the batteries did die once so I had to hand-start it once, another added reliability/safety factor. If you can accept the older 2-stroke noise/fuel consumption weaknesses it is an excellent choice in terms of reliability and performance/weight. You could discount it pretty well too and still have a great motor that will last a long time. If you did a search by motor type and problems in this board you would probably find the Tohatsu had the least problems. Servicing-- easier than most-- no oil changes.
If I were to get an expensive engine I would consider a 4-stroke EFI or a 2-stroke DFI. I would discount the boat for a Tohatsu 2-stroke and take one of those too. You could take the saved money and buy a new motor, but if you wait for the Tohatsu to fail you will be waiting a long time.
My biggest money pit while I owned my boat (sold last month) was the trailer, by far. I ended up upgrading the trailer piece by piece including rewelding galvanized steel on the entire front section, disc brakes, new brake lines, new axle, extra axle (both galvanized), new bunks and bolts, sanded down and repainted entire trailer with special rust preventative paint and sealer. It cost several thousand dollars and much time. In retrospect it would have been better to just buy a new trailer day 1. The trailer now though is as tough as could be, better than new.
....Be especially careful of the tongue. Water gets in the square tongue under the coupler/brake drum and sits there. It rusts from the inside. Mine broke on the highway, fortunately uneventfully. When I redid the entire front section I had the crossover safety chains put on properly so that they correctly support the trailer in case of a hitch failure or decoupling. The stock drum brakes get rust fouled easily as well. Disc brakes are far superior for longevity, maintaining, reliability (due to seizures on the drums), and heat dissapation.
If the trailer is questionable you will find yourself spending a lot of time keeping the trailer alive, the whole time worrying if it will hold up or you will spend a lot of money to upgrade/fix it or replace it. Some people here take care of their trailers religiously and they are probably in decent shape-- that is what you want, or a big discount on the price to replace/repair the trailer.
The boat itself is the easiest part-- no external holes---it will float. Sail condition, mods (as Frank mentioned), check the functionality of things and the holes drilled for fit/finish. Even if the C/B is sticky it is a good idea to drop it and replace the line anyway to ensure it is good. That has to be done about every 4 or 5 years depending on how much it is in the water. If it is sticking you can clean out the trunk then also. It isn't too hard to do.