Weird audio question

I am working with my father to get some music into his 42' Ocean Alexander. He has a basic CD deck in the salon. It will be running a set of in ceiling speakers and a couple speakers down in the stateroom area. Instead of trying to run an amp and a remote up to the fly bridge I think we are just going to buy another cheap deck to put up there and run 2 speakers off the deck. My question is I was walking by a garage sale today and they had a set of brand new in the box boston acoustics in ceiling home stereo speakers. They were $10 so I said what the hell and picked them up. They are 6.5" coaxials but the hang up is they are 8 ohm. Can I run them off of the deck power even though it will be 4 channels and 4 ohm? Is there anyway to use all 4 channels to the 2 speakers and make them run 4 ohm? Will it damage the deck if I just run 2 of the channels to the the 2 speakers like normal? Can I bridge the deck channels together and run them at 8 ohms to get the same amount of power to the speakers as I would running a pair of 4 ohm speakers?