i can also recommend mark towersy.
i had a coil go on my 115 optimax, it didn't "break down" as such, it just went pop, i was cruising at 22 knots at the time and it felt like we had hit something, symptoms were as you describe in the fact, the engine started fine, idled fine, revved out of gear fine but when under load the power of the cylinder with the duff coil was not available thus limiting rpm and speed,
mark diagnosed it quickly, got the parts within a few days and fitted them. Thankfully mine was done under warranty as they are expensive parts
mike (hopeyougetitsortedothermikegivemarkaring)