When my family owned A110, we fitted a Yanmar YSE8 (YSM8 and YSL8 were later versions of the same).  We had to lift the floor about 3cm where the floor hinges. The engine is single cylinder horizontal, and the highest point is the flywheel housing. Noisy, very economical (under 1litre per hour at normal cruising speed), and super-reliable once we replaced the ater pump impellor with a Jabsco part as the original Yanmar part lasted a few hours before failing.  Perfect for the boat. one problem – new ones have not been made for many years.  However, I have seen a few years ago an advertisement from a guy somewhere in northern France who used to (and maybe still does) rebuild them.  A few hours with Google should help you find him.  8HP is enough, only once not enough – around Alderney after poor navigation by me! (There is also a YSE12 but in my opinion not necessary) The engine is still fitted to the boat which is now in Germany near the mouth of river Ems. I will have a quick look for the frenchman and post if I find him. regards Richard Salter