both myself and a freind converted a few meco engines about 15-20 years ago, one was in a boat ( but not mine so dont know much about that) , the rest were for planes, it was a real botch job as nothing was purchased to do it apart from the spark plug and some 2stoke oil ( even the petrol was syphoned out of MY car )
We made a split collet to fit around the front of the crankcase out of a bit of alloy block, using a drill and a hacksaw....., used a bolt to tighten it up so it fitted onto the front of the engine, a nail was inserted into a hole in it as a handle to allow it to be turned to alter the timing, a microswitch was fitted to it, with a condenser fitted accross the terminals ( i think, but maybe from one contact to earth?, not sure!) , the microswitch was operated by a bal bearing that was glued into a hole drilled in the prop driver, coil was from a ford cortina, batteries from a model car....
It took a few goes to get the timing right as the microswitch was the wromng type it had to be off when pressed ( couold have been on, one way it was wrong!)
It ran fine , i had a merco 60 ( i think it was a 60 ) on a large vintage model once i bought a mini coil from a swapmeet , it ran a much bigger prop as petrol power than glow
It was a real botch job , using no decent tools and it worked so it must be easy to do well using tools
