prajyot

Sorry but I am not an expert in the area of ring gears or outboards. The best I can do is to confirm that all the major outboard companies produce models with electric start. Generally any engine from +/- 15 HP or larger will have electric start as the main or optional feature. The main outboard companies I know are:

USA: Johnson, Evinrude, Mercury
Japan: Yamaha, Honda, Suzuki, Tohatsu

Since these companies are all very large my guess is that they would manufacture all of their own parts but the only way to know is to contact them directly.

Good luck.