Ok, also this boat only has a 15"x17 prop on a 260hp 350 Merc. Does that sound right?

Most of the suggestions given are good ones.

Since your a newbie, let me tell you this, do not let go of the steering wheel in a boat ! The drive will want to turn (and your steering wheel) on it's own.

Did I mention - do not let go of your steering wheel while driving?? !!

I had a little skiff when I was younger with a 40 Mariner on it. I adjusted the lil fin several times and though it lessened it, it would still pull to the left.

We were skiing one time and decided to see what it would do.

Well, we were not going very fast (prob barely on plane) but it took a hard left, skipped and landed which threw a buddy out the boat.

DO NOT TRY IT!!

Luckily no one was hurt and since we were going so slow, it didn't really do anything besides throw my buddy out who wasn't holding on like I told him.

Guessing it has power steering right ? try sitting out if gear, center the wheel, rev the engine a few times, see if wheel trys to move sitting still..if it does the issue is in the P/S control valve and going to have to replace that(where cable & P/S lines connect at transom..

Good idea^^. Didn't think of that one!