I had the 4LHA engine in the same boat you are looking at. Yes, it is wet. A semi displacement hull in this size range is always going to be wet if you run in the chop on plane with any sort of crosswind. Why? Because the front half of the hull is going THROUGH the weather/water, not over it. If you go through it, spray will occur. If there is a crosswind, that spray is coming over the boat.
Yes it is noisy because you are standing on top of the engine and Mainship did not really use a lot of sound dampening material. Also as someone said, the noise is more harmonic(vibration thru the hull) than it is engine noise.
If any of these two things really bother you, I would suggest spray rails and flexible engine mounts and couplings. It didn't bother me and I would assume the 4 banger would be louder and with more vibration...just a guess.
Overall it is an excellent boat IMO. I LOVED it. My only reason for selling is I wanted more amenities/space. Otherwise, for a day application(and shorter overnighting), I don't think it can be beat. I say shorter overnighting is because I think it would a stretch in the comfort department to go for more than a weekend. I was not fond of the interior set up and liked the older setup of a V-bert instead of the (marketing department's) fold out queen. Having to build and stow that bed is a pain in the butt and it is wickedly uncomfortable. It just takes up too much space especially when stowed...it cuts off the forward 8 feet of the interior of the boat. It is usually where you stow all of your crap when aboard...just throw it up there forward. Well guess what? That crap has to find a place when the bed is deployed....so you end up with crap EVERYWHERE!!!! Anyway, just opinions of an owner for 6 years. If you have visions of extensive traveling, have a storage strategy or just be a minimalist.
It is a great sea boat. It is easy to maintain. And it is awfully efficient for a planing 30 foot boat. If you search this site, I have reviewed this boat extensively and probably more than once.
I have nothing but great things to say about the boat except interior space. Realistically, the vast majority of us use our boats in a day application. It is about the best day boat good money can buy.