Fuel, Spark, and compression is all an outboard needs. The most important in buying a used engine is compression, the other 2 are not a big deal as long as the engine has compression. The worst thing for an outboard is to sit and not be ran...I have messed with so many outboards and if they sit the carbs are always a little gummy. I actually worked on a friends last weekend and the prob with it was a old metal gas tank that was rusty and clogging up the carb. outboards can be so finicky. I believe a force is pretty easy to get parts for and not real pricey... as long as the compression test good ( all cylinders within 8-10 PSI of each other) it would probably be a great engine. I agree with Brian B, nothing beats a Yamaha they are just smooth reliable power. although we do have a Nissan 18hp that's a 1994 that has more hours on it that we could ever count. it has been the best outboard I have ever messed with. the Japs make a hell of a motor. I think a lot of it is how the previous owners has maintained it just my 2 cents