You reeeeally do not want to underpower your boat and anything less than a minimum of 200hp will do just that. 2 things come to mind if I were in a similar situation. 1 is the F225 corrosion issue; you can find deals good low hour F225's just because of the corrosion concern and association even for ones that have been repaired or don't have the problem. They can be inspected and if good, there should be a screaming deal. But what I would really look for is someone upgrading to the new Yamaha Offshore series with good, solid low hour F250's to sell. I've read over and over and over from guys that are doing this upgrade and trying to sell the F250's before having to trade them in. They have to upgrade controls and everything in the process so rigging and all goes with the sale. Just make sure to get a survey on any used power you get.
Also as has been mentioned, I would keep a sharp look out for used Etecs. I think they're great motors from what I've read; personally I just don't want to deal with oil but that in itself is why they're harder to sell and why you're likely to find a deal on one. I would not put that 150 on there; you can find something, maybe even cheaper that would fit the boat much better.
Sorry, one last thing. I see you're thinking along the lines that lighter mean more efficient. That's nearly never the case with boats; when you get the right power, you'll get better economy. With the right power, you'll pop up on plane faster and the engine doesn't struggle to do it's job. Underpower and you'll keep the throttle buried constantly trying to keep it in on plane.
Also as has been mentioned, I would keep a sharp look out for used Etecs. I think they're great motors from what I've read; personally I just don't want to deal with oil but that in itself is why they're harder to sell and why you're likely to find a deal on one. I would not put that 150 on there; you can find something, maybe even cheaper that would fit the boat much better.
Sorry, one last thing. I see you're thinking along the lines that lighter mean more efficient. That's nearly never the case with boats; when you get the right power, you'll get better economy. With the right power, you'll pop up on plane faster and the engine doesn't struggle to do it's job. Underpower and you'll keep the throttle buried constantly trying to keep it in on plane.