Starters are cheap and yes they do that. You’ll have to get a gasket and a starter. Lots of places selling Onan parts online. Amazon sells everything. Google Onan parts and you should be able to get what you need.
Here’s a good source for Onan parts. Don’t know if you can get that gasket though.
I buy direct from Cummins-Onan and some other sources like this place occasionally
https://www.partsfortechs.com/asapcart/