[willy]

I beleive Ozzie is referring to the fact that the motor has been sitting for a long time more than the brand. Those motors were decent if maintained and a 150 two stroke is just about the perfect engine for a V20. Ten years if not taken care of and especially if it was not put away correctly usually means major work on the engine but you may luck out.
You will have to go into it on the assumption that the motor is shot and figure from there. A 90 V20 is a good model year I believe, they all have wood in their construction right up till the last one made. That means transom and stringers, bulkheads by the cuddy entrance especially seems to be a problem area if water is allowed to seep in.
I believe also you will have a plastic tank not aluminum, somewhere around there they switched over, that is good, no corrosion but you will have to at least completely drain and flush cause there is going to be a lot of crap in there. There are commercial guys that will do that for you.
Figure all hoses and fuel lines to be replaced but that is a easy do it yourselfer
Sitting like that water will accumalate and sit against the garber plug area at the bottom of the transom, check that area good for rot for that reason.
You will have to use the motor as leverage and try to flex the transom to check for it flexing a lot or as Ozzie said making excessive snap crackle and popping.
Post some pics for us to see. We might spot something else that will help you and be more specific on where the soft spot is on the front of the boat.
If it has been sitting I would offer him less than a grand for sure, but a good used trailer would be easily worth 600-800 so it should work out well, if the boat and the motor turn out to be salvageable you are in like Flint