It won't have any effect on the motor, but the performance will be disappointing in all likelihood.

I don't think you'll like the results. The long shaft has plenty of drag, and if the motor is kind of marginal for power (and it may well be on a big 14' boat) then you'll probably be disappointed. My gut feel is that you will have trouble getting on plane. You will also throw a lot of water.

The suggestion that you raise the transom on your boat is a good one. You could do it easily enough with some 2x6 or 2x8 stock bolted across the transom and reinforced with plate and angle braces through-bolted in place. ( I'm thinking I would put a safety chain on the motor the first few times I went out..)

The upside is that by raising the level of your transom, you'd have a more seaworthy boat.

Good luck,

Keith