I just bought a brand new 2007 mercury 40hp 4 stroke. It had never been used. The dealer i bought it from had me put a 4 blade stainless prop on it with a 12 pitch. Now when im out in the water at idle there is a clanking noise. If i just barrely idle up the noise quits. The dealer says its because the prop and the spline are off just barrely. And it needs time for the prop to catch up with the spline. Is this right? Should i be worried?