Not really a problem if the prop is smacking the water when you are slow and in displacement mode, even fully submerged. I don't have a kicker on my twin engine boat, but when I had kickers on single engined boats, even if they prop was mostly submerged on the kicker, when I went onto plane at higher speeds, the kicker prop was instantly out of the water. In either case, I always put the kicker in gear to keep the prop from turning the drive train whether the kicker was in or out of the water. If you can jimmy the kicker prop out of the water with some of the suggestions, so much the better, but it shouldn't be much of a worry if you can't. Just my experience. Others will have other views.